从文件扩展名中获取 MIME 类型答案

【问题标题】：Get MIME type from filename extension从文件扩展名中获取 MIME 类型
【发布时间】：2010-11-05 00:14:42
【问题描述】：

如何从文件扩展名中获取 MIME 类型？

【问题讨论】：

我认为最好的是http://msdn.microsoft.com/en-us/library/system.web.mimemapping.aspx
@Yuki，感谢您添加新的相关信息。不幸的是，在 .NET 4.5 中可用的 MS 实现只有 195 个映射，无法添加更多，并且不可配置。我下面的列表有 560 多个映射。奇怪的是，MS 列表甚至缺少非常常见的 MS 扩展名，例如 .docx 和 .xlsx 以及其他重要的 Web 扩展名，例如 .csv、.swf 和 .air。

标签： c# asp.net mime

【解决方案1】：

对于 ASP.NET 或其他

这些选项在 ASP.NET Core 中有所更改，这里是 (credits)：

new FileExtensionContentTypeProvider().TryGetContentType(fileName, out contentType);（仅限 vNext）
- 从未测试过，但看起来您可以通过公开的 Mappings 属性正式扩展 mime 类型列表。
使用MimeTypes NuGet 包
从 .NET Framework 的 reference source 复制 MimeMappings 文件

对于 .NET Framework >= 4.5：

使用 System.Web.MimeMapping.GetMimeMapping 方法，它是 .NET Framework 4.5 中 BCL 的一部分：

string mimeType = MimeMapping.GetMimeMapping(fileName);

如果您需要添加自定义映射，您可能可以使用反射将映射添加到 BCL MimeMapping 类，它使用公开此方法的自定义字典，因此您应该调用以下命令来添加映射（从未测试过，但应该可以工作）。

无论如何，当使用反射添加 MIME 类型时，请注意，由于您访问的是私有字段，其名称可能会更改甚至完全删除，因此您应该格外小心并添加双重检查并提供故障安全操作每一步。

MimeMapping._mappingDictionary.AddMapping(string fileExtension, string mimeType)

【讨论】：

+1 用于添加新的相关信息。不幸的是，在 .NET 4.5 中可用的 MS 实现只有 195 个映射，无法添加更多，并且不可配置。我上面的清单有 560 个映射。奇怪的是，MS 列表甚至缺少非常常见的 MS 扩展，例如 .docx 和 .xlsx 以及其他重要的 Web 扩展，例如 .csv、.swf 和 .air。
@SamuelNeff 您当然可以使用反射添加映射 (MimeMapping._mappingDictionary.AddMapping(string fileExtension, string mimeType))。
在私有字段上使用反射不是一个好主意。它们将来更有可能发生变化，因为它不是商定的合同，如果发生这种情况，您将收到运行时错误而不是编译时错误。如果您打算这样做，您至少应该为其添加单元测试，以确保在升级 .NET 版本时尽早捕获它。除此之外，如果您要手动添加映射，您不妨维护自己的集合。该类只不过是字典的包装器。
当然，这将防止错误，但如果变量和方法不存在，您添加自定义映射的代码将不起作用。你不会再犯错误了。我们可以不同意和争论，最重要的是你是对的，你可以通过反射在技术上调用它，但我个人绝不建议在生产应用程序中对私有属性使用反射，除非它是绝对必要的并且如果没有适当的保护措施来及早发现它它失败了。
FWIW，System.Web 已从 ASP.NET CORE (asp.net 5) 中删除，这意味着不再有 MimeMapping。

【解决方案2】：

更新

有关许多贡献者添加的最新映射，请参阅此 GitHub 存储库：

https://github.com/samuelneff/MimeTypeMap

和 NuGet 包

https://www.nuget.org/packages/MimeTypeMapOfficial/

我发现我的应用程序使用的许多 mime 类型不在默认的 Windows 注册表中，而其他类型在注册表中但不在 IIS 包含的列表中。我已经从这些位置编译了一个列表，并添加了一些我们使用的其他位置。

编辑：查看带有 here 贡献的最新版本，包括高效且确定性的双向映射。

private static IDictionary<string, string> _mappings = new Dictionary<string, string>(StringComparer.InvariantCultureIgnoreCase) {

        #region Big freaking list of mime types
        // combination of values from Windows 7 Registry and 
        // from C:\Windows\System32\inetsrv\config\applicationHost.config
        // some added, including .7z and .dat
        {".323", "text/h323"},
        {".3g2", "video/3gpp2"},
        {".3gp", "video/3gpp"},
        {".3gp2", "video/3gpp2"},
        {".3gpp", "video/3gpp"},
        {".7z", "application/x-7z-compressed"},
        {".aa", "audio/audible"},
        {".AAC", "audio/aac"},
        {".aaf", "application/octet-stream"},
        {".aax", "audio/vnd.audible.aax"},
        {".ac3", "audio/ac3"},
        {".aca", "application/octet-stream"},
        {".accda", "application/msaccess.addin"},
        {".accdb", "application/msaccess"},
        {".accdc", "application/msaccess.cab"},
        {".accde", "application/msaccess"},
        {".accdr", "application/msaccess.runtime"},
        {".accdt", "application/msaccess"},
        {".accdw", "application/msaccess.webapplication"},
        {".accft", "application/msaccess.ftemplate"},
        {".acx", "application/internet-property-stream"},
        {".AddIn", "text/xml"},
        {".ade", "application/msaccess"},
        {".adobebridge", "application/x-bridge-url"},
        {".adp", "application/msaccess"},
        {".ADT", "audio/vnd.dlna.adts"},
        {".ADTS", "audio/aac"},
        {".afm", "application/octet-stream"},
        {".ai", "application/postscript"},
        {".aif", "audio/x-aiff"},
        {".aifc", "audio/aiff"},
        {".aiff", "audio/aiff"},
        {".air", "application/vnd.adobe.air-application-installer-package+zip"},
        {".amc", "application/x-mpeg"},
        {".application", "application/x-ms-application"},
        {".art", "image/x-jg"},
        {".asa", "application/xml"},
        {".asax", "application/xml"},
        {".ascx", "application/xml"},
        {".asd", "application/octet-stream"},
        {".asf", "video/x-ms-asf"},
        {".ashx", "application/xml"},
        {".asi", "application/octet-stream"},
        {".asm", "text/plain"},
        {".asmx", "application/xml"},
        {".aspx", "application/xml"},
        {".asr", "video/x-ms-asf"},
        {".asx", "video/x-ms-asf"},
        {".atom", "application/atom+xml"},
        {".au", "audio/basic"},
        {".avi", "video/x-msvideo"},
        {".axs", "application/olescript"},
        {".bas", "text/plain"},
        {".bcpio", "application/x-bcpio"},
        {".bin", "application/octet-stream"},
        {".bmp", "image/bmp"},
        {".c", "text/plain"},
        {".cab", "application/octet-stream"},
        {".caf", "audio/x-caf"},
        {".calx", "application/vnd.ms-office.calx"},
        {".cat", "application/vnd.ms-pki.seccat"},
        {".cc", "text/plain"},
        {".cd", "text/plain"},
        {".cdda", "audio/aiff"},
        {".cdf", "application/x-cdf"},
        {".cer", "application/x-x509-ca-cert"},
        {".chm", "application/octet-stream"},
        {".class", "application/x-java-applet"},
        {".clp", "application/x-msclip"},
        {".cmx", "image/x-cmx"},
        {".cnf", "text/plain"},
        {".cod", "image/cis-cod"},
        {".config", "application/xml"},
        {".contact", "text/x-ms-contact"},
        {".coverage", "application/xml"},
        {".cpio", "application/x-cpio"},
        {".cpp", "text/plain"},
        {".crd", "application/x-mscardfile"},
        {".crl", "application/pkix-crl"},
        {".crt", "application/x-x509-ca-cert"},
        {".cs", "text/plain"},
        {".csdproj", "text/plain"},
        {".csh", "application/x-csh"},
        {".csproj", "text/plain"},
        {".css", "text/css"},
        {".csv", "text/csv"},
        {".cur", "application/octet-stream"},
        {".cxx", "text/plain"},
        {".dat", "application/octet-stream"},
        {".datasource", "application/xml"},
        {".dbproj", "text/plain"},
        {".dcr", "application/x-director"},
        {".def", "text/plain"},
        {".deploy", "application/octet-stream"},
        {".der", "application/x-x509-ca-cert"},
        {".dgml", "application/xml"},
        {".dib", "image/bmp"},
        {".dif", "video/x-dv"},
        {".dir", "application/x-director"},
        {".disco", "text/xml"},
        {".dll", "application/x-msdownload"},
        {".dll.config", "text/xml"},
        {".dlm", "text/dlm"},
        {".doc", "application/msword"},
        {".docm", "application/vnd.ms-word.document.macroEnabled.12"},
        {".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
        {".dot", "application/msword"},
        {".dotm", "application/vnd.ms-word.template.macroEnabled.12"},
        {".dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"},
        {".dsp", "application/octet-stream"},
        {".dsw", "text/plain"},
        {".dtd", "text/xml"},
        {".dtsConfig", "text/xml"},
        {".dv", "video/x-dv"},
        {".dvi", "application/x-dvi"},
        {".dwf", "drawing/x-dwf"},
        {".dwp", "application/octet-stream"},
        {".dxr", "application/x-director"},
        {".eml", "message/rfc822"},
        {".emz", "application/octet-stream"},
        {".eot", "application/octet-stream"},
        {".eps", "application/postscript"},
        {".etl", "application/etl"},
        {".etx", "text/x-setext"},
        {".evy", "application/envoy"},
        {".exe", "application/octet-stream"},
        {".exe.config", "text/xml"},
        {".fdf", "application/vnd.fdf"},
        {".fif", "application/fractals"},
        {".filters", "Application/xml"},
        {".fla", "application/octet-stream"},
        {".flr", "x-world/x-vrml"},
        {".flv", "video/x-flv"},
        {".fsscript", "application/fsharp-script"},
        {".fsx", "application/fsharp-script"},
        {".generictest", "application/xml"},
        {".gif", "image/gif"},
        {".group", "text/x-ms-group"},
        {".gsm", "audio/x-gsm"},
        {".gtar", "application/x-gtar"},
        {".gz", "application/x-gzip"},
        {".h", "text/plain"},
        {".hdf", "application/x-hdf"},
        {".hdml", "text/x-hdml"},
        {".hhc", "application/x-oleobject"},
        {".hhk", "application/octet-stream"},
        {".hhp", "application/octet-stream"},
        {".hlp", "application/winhlp"},
        {".hpp", "text/plain"},
        {".hqx", "application/mac-binhex40"},
        {".hta", "application/hta"},
        {".htc", "text/x-component"},
        {".htm", "text/html"},
        {".html", "text/html"},
        {".htt", "text/webviewhtml"},
        {".hxa", "application/xml"},
        {".hxc", "application/xml"},
        {".hxd", "application/octet-stream"},
        {".hxe", "application/xml"},
        {".hxf", "application/xml"},
        {".hxh", "application/octet-stream"},
        {".hxi", "application/octet-stream"},
        {".hxk", "application/xml"},
        {".hxq", "application/octet-stream"},
        {".hxr", "application/octet-stream"},
        {".hxs", "application/octet-stream"},
        {".hxt", "text/html"},
        {".hxv", "application/xml"},
        {".hxw", "application/octet-stream"},
        {".hxx", "text/plain"},
        {".i", "text/plain"},
        {".ico", "image/x-icon"},
        {".ics", "application/octet-stream"},
        {".idl", "text/plain"},
        {".ief", "image/ief"},
        {".iii", "application/x-iphone"},
        {".inc", "text/plain"},
        {".inf", "application/octet-stream"},
        {".inl", "text/plain"},
        {".ins", "application/x-internet-signup"},
        {".ipa", "application/x-itunes-ipa"},
        {".ipg", "application/x-itunes-ipg"},
        {".ipproj", "text/plain"},
        {".ipsw", "application/x-itunes-ipsw"},
        {".iqy", "text/x-ms-iqy"},
        {".isp", "application/x-internet-signup"},
        {".ite", "application/x-itunes-ite"},
        {".itlp", "application/x-itunes-itlp"},
        {".itms", "application/x-itunes-itms"},
        {".itpc", "application/x-itunes-itpc"},
        {".IVF", "video/x-ivf"},
        {".jar", "application/java-archive"},
        {".java", "application/octet-stream"},
        {".jck", "application/liquidmotion"},
        {".jcz", "application/liquidmotion"},
        {".jfif", "image/pjpeg"},
        {".jnlp", "application/x-java-jnlp-file"},
        {".jpb", "application/octet-stream"},
        {".jpe", "image/jpeg"},
        {".jpeg", "image/jpeg"},
        {".jpg", "image/jpeg"},
        {".js", "application/x-javascript"},
        {".json", "application/json"},
        {".jsx", "text/jscript"},
        {".jsxbin", "text/plain"},
        {".latex", "application/x-latex"},
        {".library-ms", "application/windows-library+xml"},
        {".lit", "application/x-ms-reader"},
        {".loadtest", "application/xml"},
        {".lpk", "application/octet-stream"},
        {".lsf", "video/x-la-asf"},
        {".lst", "text/plain"},
        {".lsx", "video/x-la-asf"},
        {".lzh", "application/octet-stream"},
        {".m13", "application/x-msmediaview"},
        {".m14", "application/x-msmediaview"},
        {".m1v", "video/mpeg"},
        {".m2t", "video/vnd.dlna.mpeg-tts"},
        {".m2ts", "video/vnd.dlna.mpeg-tts"},
        {".m2v", "video/mpeg"},
        {".m3u", "audio/x-mpegurl"},
        {".m3u8", "audio/x-mpegurl"},
        {".m4a", "audio/m4a"},
        {".m4b", "audio/m4b"},
        {".m4p", "audio/m4p"},
        {".m4r", "audio/x-m4r"},
        {".m4v", "video/x-m4v"},
        {".mac", "image/x-macpaint"},
        {".mak", "text/plain"},
        {".man", "application/x-troff-man"},
        {".manifest", "application/x-ms-manifest"},
        {".map", "text/plain"},
        {".master", "application/xml"},
        {".mda", "application/msaccess"},
        {".mdb", "application/x-msaccess"},
        {".mde", "application/msaccess"},
        {".mdp", "application/octet-stream"},
        {".me", "application/x-troff-me"},
        {".mfp", "application/x-shockwave-flash"},
        {".mht", "message/rfc822"},
        {".mhtml", "message/rfc822"},
        {".mid", "audio/mid"},
        {".midi", "audio/mid"},
        {".mix", "application/octet-stream"},
        {".mk", "text/plain"},
        {".mmf", "application/x-smaf"},
        {".mno", "text/xml"},
        {".mny", "application/x-msmoney"},
        {".mod", "video/mpeg"},
        {".mov", "video/quicktime"},
        {".movie", "video/x-sgi-movie"},
        {".mp2", "video/mpeg"},
        {".mp2v", "video/mpeg"},
        {".mp3", "audio/mpeg"},
        {".mp4", "video/mp4"},
        {".mp4v", "video/mp4"},
        {".mpa", "video/mpeg"},
        {".mpe", "video/mpeg"},
        {".mpeg", "video/mpeg"},
        {".mpf", "application/vnd.ms-mediapackage"},
        {".mpg", "video/mpeg"},
        {".mpp", "application/vnd.ms-project"},
        {".mpv2", "video/mpeg"},
        {".mqv", "video/quicktime"},
        {".ms", "application/x-troff-ms"},
        {".msi", "application/octet-stream"},
        {".mso", "application/octet-stream"},
        {".mts", "video/vnd.dlna.mpeg-tts"},
        {".mtx", "application/xml"},
        {".mvb", "application/x-msmediaview"},
        {".mvc", "application/x-miva-compiled"},
        {".mxp", "application/x-mmxp"},
        {".nc", "application/x-netcdf"},
        {".nsc", "video/x-ms-asf"},
        {".nws", "message/rfc822"},
        {".ocx", "application/octet-stream"},
        {".oda", "application/oda"},
        {".odc", "text/x-ms-odc"},
        {".odh", "text/plain"},
        {".odl", "text/plain"},
        {".odp", "application/vnd.oasis.opendocument.presentation"},
        {".ods", "application/oleobject"},
        {".odt", "application/vnd.oasis.opendocument.text"},
        {".one", "application/onenote"},
        {".onea", "application/onenote"},
        {".onepkg", "application/onenote"},
        {".onetmp", "application/onenote"},
        {".onetoc", "application/onenote"},
        {".onetoc2", "application/onenote"},
        {".orderedtest", "application/xml"},
        {".osdx", "application/opensearchdescription+xml"},
        {".p10", "application/pkcs10"},
        {".p12", "application/x-pkcs12"},
        {".p7b", "application/x-pkcs7-certificates"},
        {".p7c", "application/pkcs7-mime"},
        {".p7m", "application/pkcs7-mime"},
        {".p7r", "application/x-pkcs7-certreqresp"},
        {".p7s", "application/pkcs7-signature"},
        {".pbm", "image/x-portable-bitmap"},
        {".pcast", "application/x-podcast"},
        {".pct", "image/pict"},
        {".pcx", "application/octet-stream"},
        {".pcz", "application/octet-stream"},
        {".pdf", "application/pdf"},
        {".pfb", "application/octet-stream"},
        {".pfm", "application/octet-stream"},
        {".pfx", "application/x-pkcs12"},
        {".pgm", "image/x-portable-graymap"},
        {".pic", "image/pict"},
        {".pict", "image/pict"},
        {".pkgdef", "text/plain"},
        {".pkgundef", "text/plain"},
        {".pko", "application/vnd.ms-pki.pko"},
        {".pls", "audio/scpls"},
        {".pma", "application/x-perfmon"},
        {".pmc", "application/x-perfmon"},
        {".pml", "application/x-perfmon"},
        {".pmr", "application/x-perfmon"},
        {".pmw", "application/x-perfmon"},
        {".png", "image/png"},
        {".pnm", "image/x-portable-anymap"},
        {".pnt", "image/x-macpaint"},
        {".pntg", "image/x-macpaint"},
        {".pnz", "image/png"},
        {".pot", "application/vnd.ms-powerpoint"},
        {".potm", "application/vnd.ms-powerpoint.template.macroEnabled.12"},
        {".potx", "application/vnd.openxmlformats-officedocument.presentationml.template"},
        {".ppa", "application/vnd.ms-powerpoint"},
        {".ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12"},
        {".ppm", "image/x-portable-pixmap"},
        {".pps", "application/vnd.ms-powerpoint"},
        {".ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12"},
        {".ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow"},
        {".ppt", "application/vnd.ms-powerpoint"},
        {".pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12"},
        {".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"},
        {".prf", "application/pics-rules"},
        {".prm", "application/octet-stream"},
        {".prx", "application/octet-stream"},
        {".ps", "application/postscript"},
        {".psc1", "application/PowerShell"},
        {".psd", "application/octet-stream"},
        {".psess", "application/xml"},
        {".psm", "application/octet-stream"},
        {".psp", "application/octet-stream"},
        {".pub", "application/x-mspublisher"},
        {".pwz", "application/vnd.ms-powerpoint"},
        {".qht", "text/x-html-insertion"},
        {".qhtm", "text/x-html-insertion"},
        {".qt", "video/quicktime"},
        {".qti", "image/x-quicktime"},
        {".qtif", "image/x-quicktime"},
        {".qtl", "application/x-quicktimeplayer"},
        {".qxd", "application/octet-stream"},
        {".ra", "audio/x-pn-realaudio"},
        {".ram", "audio/x-pn-realaudio"},
        {".rar", "application/octet-stream"},
        {".ras", "image/x-cmu-raster"},
        {".rat", "application/rat-file"},
        {".rc", "text/plain"},
        {".rc2", "text/plain"},
        {".rct", "text/plain"},
        {".rdlc", "application/xml"},
        {".resx", "application/xml"},
        {".rf", "image/vnd.rn-realflash"},
        {".rgb", "image/x-rgb"},
        {".rgs", "text/plain"},
        {".rm", "application/vnd.rn-realmedia"},
        {".rmi", "audio/mid"},
        {".rmp", "application/vnd.rn-rn_music_package"},
        {".roff", "application/x-troff"},
        {".rpm", "audio/x-pn-realaudio-plugin"},
        {".rqy", "text/x-ms-rqy"},
        {".rtf", "application/rtf"},
        {".rtx", "text/richtext"},
        {".ruleset", "application/xml"},
        {".s", "text/plain"},
        {".safariextz", "application/x-safari-safariextz"},
        {".scd", "application/x-msschedule"},
        {".sct", "text/scriptlet"},
        {".sd2", "audio/x-sd2"},
        {".sdp", "application/sdp"},
        {".sea", "application/octet-stream"},
        {".searchConnector-ms", "application/windows-search-connector+xml"},
        {".setpay", "application/set-payment-initiation"},
        {".setreg", "application/set-registration-initiation"},
        {".settings", "application/xml"},
        {".sgimb", "application/x-sgimb"},
        {".sgml", "text/sgml"},
        {".sh", "application/x-sh"},
        {".shar", "application/x-shar"},
        {".shtml", "text/html"},
        {".sit", "application/x-stuffit"},
        {".sitemap", "application/xml"},
        {".skin", "application/xml"},
        {".sldm", "application/vnd.ms-powerpoint.slide.macroEnabled.12"},
        {".sldx", "application/vnd.openxmlformats-officedocument.presentationml.slide"},
        {".slk", "application/vnd.ms-excel"},
        {".sln", "text/plain"},
        {".slupkg-ms", "application/x-ms-license"},
        {".smd", "audio/x-smd"},
        {".smi", "application/octet-stream"},
        {".smx", "audio/x-smd"},
        {".smz", "audio/x-smd"},
        {".snd", "audio/basic"},
        {".snippet", "application/xml"},
        {".snp", "application/octet-stream"},
        {".sol", "text/plain"},
        {".sor", "text/plain"},
        {".spc", "application/x-pkcs7-certificates"},
        {".spl", "application/futuresplash"},
        {".src", "application/x-wais-source"},
        {".srf", "text/plain"},
        {".SSISDeploymentManifest", "text/xml"},
        {".ssm", "application/streamingmedia"},
        {".sst", "application/vnd.ms-pki.certstore"},
        {".stl", "application/vnd.ms-pki.stl"},
        {".sv4cpio", "application/x-sv4cpio"},
        {".sv4crc", "application/x-sv4crc"},
        {".svc", "application/xml"},
        {".swf", "application/x-shockwave-flash"},
        {".t", "application/x-troff"},
        {".tar", "application/x-tar"},
        {".tcl", "application/x-tcl"},
        {".testrunconfig", "application/xml"},
        {".testsettings", "application/xml"},
        {".tex", "application/x-tex"},
        {".texi", "application/x-texinfo"},
        {".texinfo", "application/x-texinfo"},
        {".tgz", "application/x-compressed"},
        {".thmx", "application/vnd.ms-officetheme"},
        {".thn", "application/octet-stream"},
        {".tif", "image/tiff"},
        {".tiff", "image/tiff"},
        {".tlh", "text/plain"},
        {".tli", "text/plain"},
        {".toc", "application/octet-stream"},
        {".tr", "application/x-troff"},
        {".trm", "application/x-msterminal"},
        {".trx", "application/xml"},
        {".ts", "video/vnd.dlna.mpeg-tts"},
        {".tsv", "text/tab-separated-values"},
        {".ttf", "application/octet-stream"},
        {".tts", "video/vnd.dlna.mpeg-tts"},
        {".txt", "text/plain"},
        {".u32", "application/octet-stream"},
        {".uls", "text/iuls"},
        {".user", "text/plain"},
        {".ustar", "application/x-ustar"},
        {".vb", "text/plain"},
        {".vbdproj", "text/plain"},
        {".vbk", "video/mpeg"},
        {".vbproj", "text/plain"},
        {".vbs", "text/vbscript"},
        {".vcf", "text/x-vcard"},
        {".vcproj", "Application/xml"},
        {".vcs", "text/plain"},
        {".vcxproj", "Application/xml"},
        {".vddproj", "text/plain"},
        {".vdp", "text/plain"},
        {".vdproj", "text/plain"},
        {".vdx", "application/vnd.ms-visio.viewer"},
        {".vml", "text/xml"},
        {".vscontent", "application/xml"},
        {".vsct", "text/xml"},
        {".vsd", "application/vnd.visio"},
        {".vsi", "application/ms-vsi"},
        {".vsix", "application/vsix"},
        {".vsixlangpack", "text/xml"},
        {".vsixmanifest", "text/xml"},
        {".vsmdi", "application/xml"},
        {".vspscc", "text/plain"},
        {".vss", "application/vnd.visio"},
        {".vsscc", "text/plain"},
        {".vssettings", "text/xml"},
        {".vssscc", "text/plain"},
        {".vst", "application/vnd.visio"},
        {".vstemplate", "text/xml"},
        {".vsto", "application/x-ms-vsto"},
        {".vsw", "application/vnd.visio"},
        {".vsx", "application/vnd.visio"},
        {".vtx", "application/vnd.visio"},
        {".wav", "audio/wav"},
        {".wave", "audio/wav"},
        {".wax", "audio/x-ms-wax"},
        {".wbk", "application/msword"},
        {".wbmp", "image/vnd.wap.wbmp"},
        {".wcm", "application/vnd.ms-works"},
        {".wdb", "application/vnd.ms-works"},
        {".wdp", "image/vnd.ms-photo"},
        {".webarchive", "application/x-safari-webarchive"},
        {".webtest", "application/xml"},
        {".wiq", "application/xml"},
        {".wiz", "application/msword"},
        {".wks", "application/vnd.ms-works"},
        {".WLMP", "application/wlmoviemaker"},
        {".wlpginstall", "application/x-wlpg-detect"},
        {".wlpginstall3", "application/x-wlpg3-detect"},
        {".wm", "video/x-ms-wm"},
        {".wma", "audio/x-ms-wma"},
        {".wmd", "application/x-ms-wmd"},
        {".wmf", "application/x-msmetafile"},
        {".wml", "text/vnd.wap.wml"},
        {".wmlc", "application/vnd.wap.wmlc"},
        {".wmls", "text/vnd.wap.wmlscript"},
        {".wmlsc", "application/vnd.wap.wmlscriptc"},
        {".wmp", "video/x-ms-wmp"},
        {".wmv", "video/x-ms-wmv"},
        {".wmx", "video/x-ms-wmx"},
        {".wmz", "application/x-ms-wmz"},
        {".wpl", "application/vnd.ms-wpl"},
        {".wps", "application/vnd.ms-works"},
        {".wri", "application/x-mswrite"},
        {".wrl", "x-world/x-vrml"},
        {".wrz", "x-world/x-vrml"},
        {".wsc", "text/scriptlet"},
        {".wsdl", "text/xml"},
        {".wvx", "video/x-ms-wvx"},
        {".x", "application/directx"},
        {".xaf", "x-world/x-vrml"},
        {".xaml", "application/xaml+xml"},
        {".xap", "application/x-silverlight-app"},
        {".xbap", "application/x-ms-xbap"},
        {".xbm", "image/x-xbitmap"},
        {".xdr", "text/plain"},
        {".xht", "application/xhtml+xml"},
        {".xhtml", "application/xhtml+xml"},
        {".xla", "application/vnd.ms-excel"},
        {".xlam", "application/vnd.ms-excel.addin.macroEnabled.12"},
        {".xlc", "application/vnd.ms-excel"},
        {".xld", "application/vnd.ms-excel"},
        {".xlk", "application/vnd.ms-excel"},
        {".xll", "application/vnd.ms-excel"},
        {".xlm", "application/vnd.ms-excel"},
        {".xls", "application/vnd.ms-excel"},
        {".xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12"},
        {".xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12"},
        {".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
        {".xlt", "application/vnd.ms-excel"},
        {".xltm", "application/vnd.ms-excel.template.macroEnabled.12"},
        {".xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template"},
        {".xlw", "application/vnd.ms-excel"},
        {".xml", "text/xml"},
        {".xmta", "application/xml"},
        {".xof", "x-world/x-vrml"},
        {".XOML", "text/plain"},
        {".xpm", "image/x-xpixmap"},
        {".xps", "application/vnd.ms-xpsdocument"},
        {".xrm-ms", "text/xml"},
        {".xsc", "application/xml"},
        {".xsd", "text/xml"},
        {".xsf", "text/xml"},
        {".xsl", "text/xml"},
        {".xslt", "text/xml"},
        {".xsn", "application/octet-stream"},
        {".xss", "application/xml"},
        {".xtp", "application/octet-stream"},
        {".xwd", "image/x-xwindowdump"},
        {".z", "application/x-compress"},
        {".zip", "application/x-zip-compressed"},
        #endregion
        
        };

public static string GetMimeType(string extension)
{
    if (extension == null)
    {
        throw new ArgumentNullException("extension");
    }

    if (!extension.StartsWith("."))
    {
        extension = "." + extension;
    }
    
    string mime;
    
    return _mappings.TryGetValue(extension, out mime) ? mime : "application/octet-stream";
}

【讨论】：

不知何故，我觉得在启动时从数据文件构建关联数据结构会更明智。
嘿 pplz MSFT 现在已经实现了！ Check this
@Shimmy，很有趣。不幸的是，在 .NET 4.5 中可用的 MS 实现只有 195 个映射，无法添加更多，并且不可配置。我上面的清单有 560 个映射。奇怪的是，MS 列表甚至缺少非常常见的 MS 扩展，例如 .docx 和 .xlsx 以及其他重要的 Web 扩展，例如 .csv、.swf 和 .air。
@JonPurdy，我终于开始重构它以使用字典。
@AnthonyVO，有趣的是，我最初将它作为一个开关。实际上，当您在字符串上创建开关时，它的开销比字典要多。反编译代码。它实际上做的是创建一个指针字典，然后在字典中查找指针以跳转到该位置。因此，字典的开销实际上更少。

【解决方案3】：

你可以使用这个辅助函数：

private string GetMimeType (string fileName)
{
    string mimeType = "application/unknown";
    string ext = System.IO.Path.GetExtension(fileName).ToLower();
    Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
    if (regKey != null && regKey.GetValue("Content Type") != null)
    mimeType = regKey.GetValue("Content Type").ToString();
    return mimeType;
}

【讨论】：

请记住，您正在运行此代码的机器只会“知道”某些类型 - 例如如果机器从未安装过 PDF 阅读器，则不会列出 PDF。
是的，这有点危险，因为它来自注册表，并且可能会错过未安装软件的扩展名，例如 .xlsx 如果只有旧版本的 Office，则只有 .xls
此外，每次您需要 MIME 类型时，执行注册表查找的调用都会非常昂贵。也许如果它被缓存了，但我还是更喜欢 Samuel 写的静态字典方法。
...或者，如果您使用的是 Mono，您实际上并没有 Windows 注册表可供您使用... :)
@dadwithkids 我不确定为什么注册表查找会“慢”.. 注册表访问已经非常优化（并且必须比 HTTP 上下文本身更快）。只需在某个时候监视注册表访问，以查看每秒要求处理多少次操作。

【解决方案4】：

只是为了让Shimmy 的answer 更清楚：

var mimeType = MimeMapping.GetMimeMapping(fileName);

System.Web.dll v4.5

// Summary:
//     Returns the MIME mapping for the specified file name.
//
// Parameters:
//   fileName:
//     The file name that is used to determine the MIME type.
public static string GetMimeMapping(string fileName);

【讨论】：

var mimetype = System.Web.MimeMapping.GetMimeMapping(filenamewithext);

【解决方案5】：

我喜欢 Samuel Neff 所做的工作，但不喜欢每次都创建字典的想法和开销。

我将事物重组为开关盒。是的，你不能迭代它，但在我的例子中，我只用它来快速查找一个值。特别是因为它是在 Web 服务中完成的，所以我最不想要的就是应用程序准备其结构时的大量开销。编译器会将其转换为散列查找，因此速度会非常快。

public static string GetMimeType(string extension)
{
  if (extension == null)
    throw new ArgumentNullException("extension");

  if (extension.StartsWith("."))
    extension = extension.Substring(1);


  switch (extension.ToLower())
{
    #region Big freaking list of mime types
    case "323": return "text/h323";
    case "3g2": return "video/3gpp2";
    case "3gp": return "video/3gpp";
    case "3gp2": return "video/3gpp2";
    case "3gpp": return "video/3gpp";
    case "7z": return "application/x-7z-compressed";
    case "aa": return "audio/audible";
    case "aac": return "audio/aac";
    case "aaf": return "application/octet-stream";
    case "aax": return "audio/vnd.audible.aax";
    case "ac3": return "audio/ac3";
    case "aca": return "application/octet-stream";
    case "accda": return "application/msaccess.addin";
    case "accdb": return "application/msaccess";
    case "accdc": return "application/msaccess.cab";
    case "accde": return "application/msaccess";
    case "accdr": return "application/msaccess.runtime";
    case "accdt": return "application/msaccess";
    case "accdw": return "application/msaccess.webapplication";
    case "accft": return "application/msaccess.ftemplate";
    case "acx": return "application/internet-property-stream";
    case "addin": return "text/xml";
    case "ade": return "application/msaccess";
    case "adobebridge": return "application/x-bridge-url";
    case "adp": return "application/msaccess";
    case "adt": return "audio/vnd.dlna.adts";
    case "adts": return "audio/aac";
    case "afm": return "application/octet-stream";
    case "ai": return "application/postscript";
    case "aif": return "audio/x-aiff";
    case "aifc": return "audio/aiff";
    case "aiff": return "audio/aiff";
    case "air": return "application/vnd.adobe.air-application-installer-package+zip";
    case "amc": return "application/x-mpeg";
    case "application": return "application/x-ms-application";
    case "art": return "image/x-jg";
    case "asa": return "application/xml";
    case "asax": return "application/xml";
    case "ascx": return "application/xml";
    case "asd": return "application/octet-stream";
    case "asf": return "video/x-ms-asf";
    case "ashx": return "application/xml";
    case "asi": return "application/octet-stream";
    case "asm": return "text/plain";
    case "asmx": return "application/xml";
    case "aspx": return "application/xml";
    case "asr": return "video/x-ms-asf";
    case "asx": return "video/x-ms-asf";
    case "atom": return "application/atom+xml";
    case "au": return "audio/basic";
    case "avi": return "video/x-msvideo";
    case "axs": return "application/olescript";
    case "bas": return "text/plain";
    case "bcpio": return "application/x-bcpio";
    case "bin": return "application/octet-stream";
    case "bmp": return "image/bmp";
    case "c": return "text/plain";
    case "cab": return "application/octet-stream";
    case "caf": return "audio/x-caf";
    case "calx": return "application/vnd.ms-office.calx";
    case "cat": return "application/vnd.ms-pki.seccat";
    case "cc": return "text/plain";
    case "cd": return "text/plain";
    case "cdda": return "audio/aiff";
    case "cdf": return "application/x-cdf";
    case "cer": return "application/x-x509-ca-cert";
    case "chm": return "application/octet-stream";
    case "class": return "application/x-java-applet";
    case "clp": return "application/x-msclip";
    case "cmx": return "image/x-cmx";
    case "cnf": return "text/plain";
    case "cod": return "image/cis-cod";
    case "config": return "application/xml";
    case "contact": return "text/x-ms-contact";
    case "coverage": return "application/xml";
    case "cpio": return "application/x-cpio";
    case "cpp": return "text/plain";
    case "crd": return "application/x-mscardfile";
    case "crl": return "application/pkix-crl";
    case "crt": return "application/x-x509-ca-cert";
    case "cs": return "text/plain";
    case "csdproj": return "text/plain";
    case "csh": return "application/x-csh";
    case "csproj": return "text/plain";
    case "css": return "text/css";
    case "csv": return "text/csv";
    case "cur": return "application/octet-stream";
    case "cxx": return "text/plain";
    case "dat": return "application/octet-stream";
    case "datasource": return "application/xml";
    case "dbproj": return "text/plain";
    case "dcr": return "application/x-director";
    case "def": return "text/plain";
    case "deploy": return "application/octet-stream";
    case "der": return "application/x-x509-ca-cert";
    case "dgml": return "application/xml";
    case "dib": return "image/bmp";
    case "dif": return "video/x-dv";
    case "dir": return "application/x-director";
    case "disco": return "text/xml";
    case "dll": return "application/x-msdownload";
    case "dll.config": return "text/xml";
    case "dlm": return "text/dlm";
    case "doc": return "application/msword";
    case "docm": return "application/vnd.ms-word.document.macroenabled.12";
    case "docx": return "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
    case "dot": return "application/msword";
    case "dotm": return "application/vnd.ms-word.template.macroenabled.12";
    case "dotx": return "application/vnd.openxmlformats-officedocument.wordprocessingml.template";
    case "dsp": return "application/octet-stream";
    case "dsw": return "text/plain";
    case "dtd": return "text/xml";
    case "dtsconfig": return "text/xml";
    case "dv": return "video/x-dv";
    case "dvi": return "application/x-dvi";
    case "dwf": return "drawing/x-dwf";
    case "dwp": return "application/octet-stream";
    case "dxr": return "application/x-director";
    case "eml": return "message/rfc822";
    case "emz": return "application/octet-stream";
    case "eot": return "application/octet-stream";
    case "eps": return "application/postscript";
    case "etl": return "application/etl";
    case "etx": return "text/x-setext";
    case "evy": return "application/envoy";
    case "exe": return "application/octet-stream";
    case "exe.config": return "text/xml";
    case "fdf": return "application/vnd.fdf";
    case "fif": return "application/fractals";
    case "filters": return "application/xml";
    case "fla": return "application/octet-stream";
    case "flr": return "x-world/x-vrml";
    case "flv": return "video/x-flv";
    case "fsscript": return "application/fsharp-script";
    case "fsx": return "application/fsharp-script";
    case "generictest": return "application/xml";
    case "gif": return "image/gif";
    case "group": return "text/x-ms-group";
    case "gsm": return "audio/x-gsm";
    case "gtar": return "application/x-gtar";
    case "gz": return "application/x-gzip";
    case "h": return "text/plain";
    case "hdf": return "application/x-hdf";
    case "hdml": return "text/x-hdml";
    case "hhc": return "application/x-oleobject";
    case "hhk": return "application/octet-stream";
    case "hhp": return "application/octet-stream";
    case "hlp": return "application/winhlp";
    case "hpp": return "text/plain";
    case "hqx": return "application/mac-binhex40";
    case "hta": return "application/hta";
    case "htc": return "text/x-component";
    case "htm": return "text/html";
    case "html": return "text/html";
    case "htt": return "text/webviewhtml";
    case "hxa": return "application/xml";
    case "hxc": return "application/xml";
    case "hxd": return "application/octet-stream";
    case "hxe": return "application/xml";
    case "hxf": return "application/xml";
    case "hxh": return "application/octet-stream";
    case "hxi": return "application/octet-stream";
    case "hxk": return "application/xml";
    case "hxq": return "application/octet-stream";
    case "hxr": return "application/octet-stream";
    case "hxs": return "application/octet-stream";
    case "hxt": return "text/html";
    case "hxv": return "application/xml";
    case "hxw": return "application/octet-stream";
    case "hxx": return "text/plain";
    case "i": return "text/plain";
    case "ico": return "image/x-icon";
    case "ics": return "application/octet-stream";
    case "idl": return "text/plain";
    case "ief": return "image/ief";
    case "iii": return "application/x-iphone";
    case "inc": return "text/plain";
    case "inf": return "application/octet-stream";
    case "inl": return "text/plain";
    case "ins": return "application/x-internet-signup";
    case "ipa": return "application/x-itunes-ipa";
    case "ipg": return "application/x-itunes-ipg";
    case "ipproj": return "text/plain";
    case "ipsw": return "application/x-itunes-ipsw";
    case "iqy": return "text/x-ms-iqy";
    case "isp": return "application/x-internet-signup";
    case "ite": return "application/x-itunes-ite";
    case "itlp": return "application/x-itunes-itlp";
    case "itms": return "application/x-itunes-itms";
    case "itpc": return "application/x-itunes-itpc";
    case "ivf": return "video/x-ivf";
    case "jar": return "application/java-archive";
    case "java": return "application/octet-stream";
    case "jck": return "application/liquidmotion";
    case "jcz": return "application/liquidmotion";
    case "jfif": return "image/pjpeg";
    case "jnlp": return "application/x-java-jnlp-file";
    case "jpb": return "application/octet-stream";
    case "jpe": return "image/jpeg";
    case "jpeg": return "image/jpeg";
    case "jpg": return "image/jpeg";
    case "js": return "application/x-javascript";
    case "jsx": return "text/jscript";
    case "jsxbin": return "text/plain";
    case "latex": return "application/x-latex";
    case "library-ms": return "application/windows-library+xml";
    case "lit": return "application/x-ms-reader";
    case "loadtest": return "application/xml";
    case "lpk": return "application/octet-stream";
    case "lsf": return "video/x-la-asf";
    case "lst": return "text/plain";
    case "lsx": return "video/x-la-asf";
    case "lzh": return "application/octet-stream";
    case "m13": return "application/x-msmediaview";
    case "m14": return "application/x-msmediaview";
    case "m1v": return "video/mpeg";
    case "m2t": return "video/vnd.dlna.mpeg-tts";
    case "m2ts": return "video/vnd.dlna.mpeg-tts";
    case "m2v": return "video/mpeg";
    case "m3u": return "audio/x-mpegurl";
    case "m3u8": return "audio/x-mpegurl";
    case "m4a": return "audio/m4a";
    case "m4b": return "audio/m4b";
    case "m4p": return "audio/m4p";
    case "m4r": return "audio/x-m4r";
    case "m4v": return "video/x-m4v";
    case "mac": return "image/x-macpaint";
    case "mak": return "text/plain";
    case "man": return "application/x-troff-man";
    case "manifest": return "application/x-ms-manifest";
    case "map": return "text/plain";
    case "master": return "application/xml";
    case "mda": return "application/msaccess";
    case "mdb": return "application/x-msaccess";
    case "mde": return "application/msaccess";
    case "mdp": return "application/octet-stream";
    case "me": return "application/x-troff-me";
    case "mfp": return "application/x-shockwave-flash";
    case "mht": return "message/rfc822";
    case "mhtml": return "message/rfc822";
    case "mid": return "audio/mid";
    case "midi": return "audio/mid";
    case "mix": return "application/octet-stream";
    case "mk": return "text/plain";
    case "mmf": return "application/x-smaf";
    case "mno": return "text/xml";
    case "mny": return "application/x-msmoney";
    case "mod": return "video/mpeg";
    case "mov": return "video/quicktime";
    case "movie": return "video/x-sgi-movie";
    case "mp2": return "video/mpeg";
    case "mp2v": return "video/mpeg";
    case "mp3": return "audio/mpeg";
    case "mp4": return "video/mp4";
    case "mp4v": return "video/mp4";
    case "mpa": return "video/mpeg";
    case "mpe": return "video/mpeg";
    case "mpeg": return "video/mpeg";
    case "mpf": return "application/vnd.ms-mediapackage";
    case "mpg": return "video/mpeg";
    case "mpp": return "application/vnd.ms-project";
    case "mpv2": return "video/mpeg";
    case "mqv": return "video/quicktime";
    case "ms": return "application/x-troff-ms";
    case "msi": return "application/octet-stream";
    case "mso": return "application/octet-stream";
    case "mts": return "video/vnd.dlna.mpeg-tts";
    case "mtx": return "application/xml";
    case "mvb": return "application/x-msmediaview";
    case "mvc": return "application/x-miva-compiled";
    case "mxp": return "application/x-mmxp";
    case "nc": return "application/x-netcdf";
    case "nsc": return "video/x-ms-asf";
    case "nws": return "message/rfc822";
    case "ocx": return "application/octet-stream";
    case "oda": return "application/oda";
    case "odc": return "text/x-ms-odc";
    case "odh": return "text/plain";
    case "odl": return "text/plain";
    case "odp": return "application/vnd.oasis.opendocument.presentation";
    case "ods": return "application/oleobject";
    case "odt": return "application/vnd.oasis.opendocument.text";
    case "one": return "application/onenote";
    case "onea": return "application/onenote";
    case "onepkg": return "application/onenote";
    case "onetmp": return "application/onenote";
    case "onetoc": return "application/onenote";
    case "onetoc2": return "application/onenote";
    case "orderedtest": return "application/xml";
    case "osdx": return "application/opensearchdescription+xml";
    case "p10": return "application/pkcs10";
    case "p12": return "application/x-pkcs12";
    case "p7b": return "application/x-pkcs7-certificates";
    case "p7c": return "application/pkcs7-mime";
    case "p7m": return "application/pkcs7-mime";
    case "p7r": return "application/x-pkcs7-certreqresp";
    case "p7s": return "application/pkcs7-signature";
    case "pbm": return "image/x-portable-bitmap";
    case "pcast": return "application/x-podcast";
    case "pct": return "image/pict";
    case "pcx": return "application/octet-stream";
    case "pcz": return "application/octet-stream";
    case "pdf": return "application/pdf";
    case "pfb": return "application/octet-stream";
    case "pfm": return "application/octet-stream";
    case "pfx": return "application/x-pkcs12";
    case "pgm": return "image/x-portable-graymap";
    case "pic": return "image/pict";
    case "pict": return "image/pict";
    case "pkgdef": return "text/plain";
    case "pkgundef": return "text/plain";
    case "pko": return "application/vnd.ms-pki.pko";
    case "pls": return "audio/scpls";
    case "pma": return "application/x-perfmon";
    case "pmc": return "application/x-perfmon";
    case "pml": return "application/x-perfmon";
    case "pmr": return "application/x-perfmon";
    case "pmw": return "application/x-perfmon";
    case "png": return "image/png";
    case "pnm": return "image/x-portable-anymap";
    case "pnt": return "image/x-macpaint";
    case "pntg": return "image/x-macpaint";
    case "pnz": return "image/png";
    case "pot": return "application/vnd.ms-powerpoint";
    case "potm": return "application/vnd.ms-powerpoint.template.macroenabled.12";
    case "potx": return "application/vnd.openxmlformats-officedocument.presentationml.template";
    case "ppa": return "application/vnd.ms-powerpoint";
    case "ppam": return "application/vnd.ms-powerpoint.addin.macroenabled.12";
    case "ppm": return "image/x-portable-pixmap";
    case "pps": return "application/vnd.ms-powerpoint";
    case "ppsm": return "application/vnd.ms-powerpoint.slideshow.macroenabled.12";
    case "ppsx": return "application/vnd.openxmlformats-officedocument.presentationml.slideshow";
    case "ppt": return "application/vnd.ms-powerpoint";
    case "pptm": return "application/vnd.ms-powerpoint.presentation.macroenabled.12";
    case "pptx": return "application/vnd.openxmlformats-officedocument.presentationml.presentation";
    case "prf": return "application/pics-rules";
    case "prm": return "application/octet-stream";
    case "prx": return "application/octet-stream";
    case "ps": return "application/postscript";
    case "psc1": return "application/powershell";
    case "psd": return "application/octet-stream";
    case "psess": return "application/xml";
    case "psm": return "application/octet-stream";
    case "psp": return "application/octet-stream";
    case "pub": return "application/x-mspublisher";
    case "pwz": return "application/vnd.ms-powerpoint";
    case "qht": return "text/x-html-insertion";
    case "qhtm": return "text/x-html-insertion";
    case "qt": return "video/quicktime";
    case "qti": return "image/x-quicktime";
    case "qtif": return "image/x-quicktime";
    case "qtl": return "application/x-quicktimeplayer";
    case "qxd": return "application/octet-stream";
    case "ra": return "audio/x-pn-realaudio";
    case "ram": return "audio/x-pn-realaudio";
    case "rar": return "application/octet-stream";
    case "ras": return "image/x-cmu-raster";
    case "rat": return "application/rat-file";
    case "rc": return "text/plain";
    case "rc2": return "text/plain";
    case "rct": return "text/plain";
    case "rdlc": return "application/xml";
    case "resx": return "application/xml";
    case "rf": return "image/vnd.rn-realflash";
    case "rgb": return "image/x-rgb";
    case "rgs": return "text/plain";
    case "rm": return "application/vnd.rn-realmedia";
    case "rmi": return "audio/mid";
    case "rmp": return "application/vnd.rn-rn_music_package";
    case "roff": return "application/x-troff";
    case "rpm": return "audio/x-pn-realaudio-plugin";
    case "rqy": return "text/x-ms-rqy";
    case "rtf": return "application/rtf";
    case "rtx": return "text/richtext";
    case "ruleset": return "application/xml";
    case "s": return "text/plain";
    case "safariextz": return "application/x-safari-safariextz";
    case "scd": return "application/x-msschedule";
    case "sct": return "text/scriptlet";
    case "sd2": return "audio/x-sd2";
    case "sdp": return "application/sdp";
    case "sea": return "application/octet-stream";
    case "searchconnector-ms": return "application/windows-search-connector+xml";
    case "setpay": return "application/set-payment-initiation";
    case "setreg": return "application/set-registration-initiation";
    case "settings": return "application/xml";
    case "sgimb": return "application/x-sgimb";
    case "sgml": return "text/sgml";
    case "sh": return "application/x-sh";
    case "shar": return "application/x-shar";
    case "shtml": return "text/html";
    case "sit": return "application/x-stuffit";
    case "sitemap": return "application/xml";
    case "skin": return "application/xml";
    case "sldm": return "application/vnd.ms-powerpoint.slide.macroenabled.12";
    case "sldx": return "application/vnd.openxmlformats-officedocument.presentationml.slide";
    case "slk": return "application/vnd.ms-excel";
    case "sln": return "text/plain";
    case "slupkg-ms": return "application/x-ms-license";
    case "smd": return "audio/x-smd";
    case "smi": return "application/octet-stream";
    case "smx": return "audio/x-smd";
    case "smz": return "audio/x-smd";
    case "snd": return "audio/basic";
    case "snippet": return "application/xml";
    case "snp": return "application/octet-stream";
    case "sol": return "text/plain";
    case "sor": return "text/plain";
    case "spc": return "application/x-pkcs7-certificates";
    case "spl": return "application/futuresplash";
    case "src": return "application/x-wais-source";
    case "srf": return "text/plain";
    case "ssisdeploymentmanifest": return "text/xml";
    case "ssm": return "application/streamingmedia";
    case "sst": return "application/vnd.ms-pki.certstore";
    case "stl": return "application/vnd.ms-pki.stl";
    case "sv4cpio": return "application/x-sv4cpio";
    case "sv4crc": return "application/x-sv4crc";
    case "svc": return "application/xml";
    case "swf": return "application/x-shockwave-flash";
    case "t": return "application/x-troff";
    case "tar": return "application/x-tar";
    case "tcl": return "application/x-tcl";
    case "testrunconfig": return "application/xml";
    case "testsettings": return "application/xml";
    case "tex": return "application/x-tex";
    case "texi": return "application/x-texinfo";
    case "texinfo": return "application/x-texinfo";
    case "tgz": return "application/x-compressed";
    case "thmx": return "application/vnd.ms-officetheme";
    case "thn": return "application/octet-stream";
    case "tif": return "image/tiff";
    case "tiff": return "image/tiff";
    case "tlh": return "text/plain";
    case "tli": return "text/plain";
    case "toc": return "application/octet-stream";
    case "tr": return "application/x-troff";
    case "trm": return "application/x-msterminal";
    case "trx": return "application/xml";
    case "ts": return "video/vnd.dlna.mpeg-tts";
    case "tsv": return "text/tab-separated-values";
    case "ttf": return "application/octet-stream";
    case "tts": return "video/vnd.dlna.mpeg-tts";
    case "txt": return "text/plain";
    case "u32": return "application/octet-stream";
    case "uls": return "text/iuls";
    case "user": return "text/plain";
    case "ustar": return "application/x-ustar";
    case "vb": return "text/plain";
    case "vbdproj": return "text/plain";
    case "vbk": return "video/mpeg";
    case "vbproj": return "text/plain";
    case "vbs": return "text/vbscript";
    case "vcf": return "text/x-vcard";
    case "vcproj": return "application/xml";
    case "vcs": return "text/plain";
    case "vcxproj": return "application/xml";
    case "vddproj": return "text/plain";
    case "vdp": return "text/plain";
    case "vdproj": return "text/plain";
    case "vdx": return "application/vnd.ms-visio.viewer";
    case "vml": return "text/xml";
    case "vscontent": return "application/xml";
    case "vsct": return "text/xml";
    case "vsd": return "application/vnd.visio";
    case "vsi": return "application/ms-vsi";
    case "vsix": return "application/vsix";
    case "vsixlangpack": return "text/xml";
    case "vsixmanifest": return "text/xml";
    case "vsmdi": return "application/xml";
    case "vspscc": return "text/plain";
    case "vss": return "application/vnd.visio";
    case "vsscc": return "text/plain";
    case "vssettings": return "text/xml";
    case "vssscc": return "text/plain";
    case "vst": return "application/vnd.visio";
    case "vstemplate": return "text/xml";
    case "vsto": return "application/x-ms-vsto";
    case "vsw": return "application/vnd.visio";
    case "vsx": return "application/vnd.visio";
    case "vtx": return "application/vnd.visio";
    case "wav": return "audio/wav";
    case "wave": return "audio/wav";
    case "wax": return "audio/x-ms-wax";
    case "wbk": return "application/msword";
    case "wbmp": return "image/vnd.wap.wbmp";
    case "wcm": return "application/vnd.ms-works";
    case "wdb": return "application/vnd.ms-works";
    case "wdp": return "image/vnd.ms-photo";
    case "webarchive": return "application/x-safari-webarchive";
    case "webtest": return "application/xml";
    case "wiq": return "application/xml";
    case "wiz": return "application/msword";
    case "wks": return "application/vnd.ms-works";
    case "wlmp": return "application/wlmoviemaker";
    case "wlpginstall": return "application/x-wlpg-detect";
    case "wlpginstall3": return "application/x-wlpg3-detect";
    case "wm": return "video/x-ms-wm";
    case "wma": return "audio/x-ms-wma";
    case "wmd": return "application/x-ms-wmd";
    case "wmf": return "application/x-msmetafile";
    case "wml": return "text/vnd.wap.wml";
    case "wmlc": return "application/vnd.wap.wmlc";
    case "wmls": return "text/vnd.wap.wmlscript";
    case "wmlsc": return "application/vnd.wap.wmlscriptc";
    case "wmp": return "video/x-ms-wmp";
    case "wmv": return "video/x-ms-wmv";
    case "wmx": return "video/x-ms-wmx";
    case "wmz": return "application/x-ms-wmz";
    case "wpl": return "application/vnd.ms-wpl";
    case "wps": return "application/vnd.ms-works";
    case "wri": return "application/x-mswrite";
    case "wrl": return "x-world/x-vrml";
    case "wrz": return "x-world/x-vrml";
    case "wsc": return "text/scriptlet";
    case "wsdl": return "text/xml";
    case "wvx": return "video/x-ms-wvx";
    case "x": return "application/directx";
    case "xaf": return "x-world/x-vrml";
    case "xaml": return "application/xaml+xml";
    case "xap": return "application/x-silverlight-app";
    case "xbap": return "application/x-ms-xbap";
    case "xbm": return "image/x-xbitmap";
    case "xdr": return "text/plain";
    case "xht": return "application/xhtml+xml";
    case "xhtml": return "application/xhtml+xml";
    case "xla": return "application/vnd.ms-excel";
    case "xlam": return "application/vnd.ms-excel.addin.macroenabled.12";
    case "xlc": return "application/vnd.ms-excel";
    case "xld": return "application/vnd.ms-excel";
    case "xlk": return "application/vnd.ms-excel";
    case "xll": return "application/vnd.ms-excel";
    case "xlm": return "application/vnd.ms-excel";
    case "xls": return "application/vnd.ms-excel";
    case "xlsb": return "application/vnd.ms-excel.sheet.binary.macroenabled.12";
    case "xlsm": return "application/vnd.ms-excel.sheet.macroenabled.12";
    case "xlsx": return "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    case "xlt": return "application/vnd.ms-excel";
    case "xltm": return "application/vnd.ms-excel.template.macroenabled.12";
    case "xltx": return "application/vnd.openxmlformats-officedocument.spreadsheetml.template";
    case "xlw": return "application/vnd.ms-excel";
    case "xml": return "text/xml";
    case "xmta": return "application/xml";
    case "xof": return "x-world/x-vrml";
    case "xoml": return "text/plain";
    case "xpm": return "image/x-xpixmap";
    case "xps": return "application/vnd.ms-xpsdocument";
    case "xrm-ms": return "text/xml";
    case "xsc": return "application/xml";
    case "xsd": return "text/xml";
    case "xsf": return "text/xml";
    case "xsl": return "text/xml";
    case "xslt": return "text/xml";
    case "xsn": return "application/octet-stream";
    case "xss": return "application/xml";
    case "xtp": return "application/octet-stream";
    case "xwd": return "image/x-xwindowdump";
    case "z": return "application/x-compress";
    case "zip": return "application/x-zip-compressed";
  #endregion
    default: return "application/octet-stream";
  }
}

【讨论】：

有人有这个函数的逆吗？按 mime 类型设置扩展名？只是懒惰：P
@FabioG 我不确定这对你是否有用。例如，MIME 类型“application/xml”将有来自该列表的 43 个匹配的扩展名。
@Barrie 你能做类似的事情吗：简单地使用列表中的第一个，以获得标准扩展名（最小公分母的刺），例如"application/xml" => .xml 和 "image/jpeg" =>.jpg 可以在大多数操作系统上运行，不是吗？我错过了什么？猜测这对于某些标准类型会很好，但在这个长长的列表中却失败了很多。想法？
只需将其设为静态即可避免开销。然而，当涉及到“开销”时，带有字符串的开关盒是一件可怕的事情。简单来说......在处理器层面，一切都只是检查和跳转； if/else, while, for... 这些都不存在。 switch/case，然而，应用于通常在枚举中找到的小整数值，确实存在。这是一个非常优雅的小手术。它也根本不适用于字符串，这意味着你写的实际上只是一堆字符串比较。任何一天，一个 Dictionary 对象都能胜过。
@Nyerguds，我不相信你的断言是正确的。请参阅：stackoverflow.com/a/395965/438458，另请参阅 Jon Skeet 对答案的评论。基本上，编译器比你想象的要聪明。

【解决方案6】：

您可以在注册表中找到该信息。例如，.pdf 文件的 MIME 类型可以在键 HKEY_CLASSES_ROOT\.pdf 的值“Content Type”中找到：

string mimeType = Registry.GetValue(@"HKEY_CLASSES_ROOT\.pdf", "Content Type", null) as string;

【讨论】：

如果您使用的是 Windows，可以。基本思想是“找到提供此信息的位置”，并将其导入某种数据结构中。
OP 与 ASP.NET 相关...好的，由于 Mono，ASP.NET 可以在 Linux 上运行，但这不是一个很常见的场景，所以我认为假设是相当安全的acidzombie24 正在使用 Windows...
在谈论 ASP.NET 时我会假设 Windows 是给定的，而不是指定使用 Linux。
谨慎使用此解决方案，因为结果取决于客户端安装的软件。即没有 Office，.doc 没有任何内容类型。
是的，马克说得对。似乎我需要为 .PDF 安装 Adobe Acrobat 来查找 mimetype（在 Windows Server 2008 R2 上尝试过）。因此，与扩展关联的程序似乎维护了这种 mimetype（不是 windows）。

【解决方案7】：

我编写了一个程序来获取 Apache mime.types file 并将其转换为由文件扩展名键入的 C# Dictionary<string, string>。我是here。

实际输出为this file（但您可能需要获取它并再次运行它，以防我上次运行后Apache 文件已更新）。

public static Dictionary<string, string> MimeTypes = new Dictionary<string, string>
{
  { "123", "application/vnd.lotus-1-2-3" },
  { "3dml", "text/vnd.in3d.3dml" },
  { "3g2", "video/3gpp2" },
  { "3gp", "video/3gpp" },
  { "7z", "application/x-7z-compressed" },
  { "aab", "application/x-authorware-bin" },
  { "aac", "audio/x-aac" },
  { "aam", "application/x-authorware-map" },
  { "aas", "application/x-authorware-seg" },
  { "abw", "application/x-abiword" },
  ...

【讨论】：

哦，真漂亮！我可能会反过来做类似的事情；生成一个类，其中每个 mime 类型的 Dictionary<String,String[]> 及其所有扩展名。它对于根据提交的内容类型检查下载并在需要时添加默认扩展很有用。
@Nyerguds 这听起来很有用。如果您想做 PR 以将其添加到上述内容中，我很乐意将其合并。或者你当然可以做你自己的事！但是这两个方向听起来确实很有用。
主要问题似乎是“默认”部分……在这些 mime 类型的许多扩展中，哪一个是理想的默认值。无论如何，我可能不得不硬编码这些列表

【解决方案8】：

我知道问题是针对 C# 我只想保留 Javascript 格式，因为我刚刚转换了 Samuel 的答案：

export const contentTypes = {

".323": "text/h323",
".3g2": "video/3gpp2",
".3gp": "video/3gpp",
".3gp2": "video/3gpp2",
".3gpp": "video/3gpp",
".7z": "application/x-7z-compressed",
".aa": "audio/audible",
".AAC": "audio/aac",
".aaf": "application/octet-stream",
".aax": "audio/vnd.audible.aax",
".ac3": "audio/ac3",
".aca": "application/octet-stream",
".accda": "application/msaccess.addin",
".accdb": "application/msaccess",
".accdc": "application/msaccess.cab",
".accde": "application/msaccess",
".accdr": "application/msaccess.runtime",
".accdt": "application/msaccess",
".accdw": "application/msaccess.webapplication",
".accft": "application/msaccess.ftemplate",
".acx": "application/internet-property-stream",
".AddIn": "text/xml",
".ade": "application/msaccess",
".adobebridge": "application/x-bridge-url",
".adp": "application/msaccess",
".ADT": "audio/vnd.dlna.adts",
".ADTS": "audio/aac",
".afm": "application/octet-stream",
".ai": "application/postscript",
".aif": "audio/x-aiff",
".aifc": "audio/aiff",
".aiff": "audio/aiff",
".air": "application/vnd.adobe.air-application-installer-package+zip",
".amc": "application/x-mpeg",
".application": "application/x-ms-application",
".art": "image/x-jg",
".asa": "application/xml",
".asax": "application/xml",
".ascx": "application/xml",
".asd": "application/octet-stream",
".asf": "video/x-ms-asf",
".ashx": "application/xml",
".asi": "application/octet-stream",
".asm": "text/plain",
".asmx": "application/xml",
".aspx": "application/xml",
".asr": "video/x-ms-asf",
".asx": "video/x-ms-asf",
".atom": "application/atom+xml",
".au": "audio/basic",
".avi": "video/x-msvideo",
".axs": "application/olescript",
".bas": "text/plain",
".bcpio": "application/x-bcpio",
".bin": "application/octet-stream",
".bmp": "image/bmp",
".c": "text/plain",
".cab": "application/octet-stream",
".caf": "audio/x-caf",
".calx": "application/vnd.ms-office.calx",
".cat": "application/vnd.ms-pki.seccat",
".cc": "text/plain",
".cd": "text/plain",
".cdda": "audio/aiff",
".cdf": "application/x-cdf",
".cer": "application/x-x509-ca-cert",
".chm": "application/octet-stream",
".class": "application/x-java-applet",
".clp": "application/x-msclip",
".cmx": "image/x-cmx",
".cnf": "text/plain",
".cod": "image/cis-cod",
".config": "application/xml",
".contact": "text/x-ms-contact",
".coverage": "application/xml",
".cpio": "application/x-cpio",
".cpp": "text/plain",
".crd": "application/x-mscardfile",
".crl": "application/pkix-crl",
".crt": "application/x-x509-ca-cert",
".cs": "text/plain",
".csdproj": "text/plain",
".csh": "application/x-csh",
".csproj": "text/plain",
".css": "text/css",
".csv": "text/csv",
".cur": "application/octet-stream",
".cxx": "text/plain",
".dat": "application/octet-stream",
".datasource": "application/xml",
".dbproj": "text/plain",
".dcr": "application/x-director",
".def": "text/plain",
".deploy": "application/octet-stream",
".der": "application/x-x509-ca-cert",
".dgml": "application/xml",
".dib": "image/bmp",
".dif": "video/x-dv",
".dir": "application/x-director",
".disco": "text/xml",
".dll": "application/x-msdownload",
".dll.config": "text/xml",
".dlm": "text/dlm",
".doc": "application/msword",
".docm": "application/vnd.ms-word.document.macroEnabled.12",
".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
".dot": "application/msword",
".dotm": "application/vnd.ms-word.template.macroEnabled.12",
".dotx": "application/vnd.openxmlformats-officedocument.wordprocessingml.template",
".dsp": "application/octet-stream",
".dsw": "text/plain",
".dtd": "text/xml",
".dtsConfig": "text/xml",
".dv": "video/x-dv",
".dvi": "application/x-dvi",
".dwf": "drawing/x-dwf",
".dwp": "application/octet-stream",
".dxr": "application/x-director",
".eml": "message/rfc822",
".emz": "application/octet-stream",
".eot": "application/octet-stream",
".eps": "application/postscript",
".etl": "application/etl",
".etx": "text/x-setext",
".evy": "application/envoy",
".exe": "application/octet-stream",
".exe.config": "text/xml",
".fdf": "application/vnd.fdf",
".fif": "application/fractals",
".filters": "Application/xml",
".fla": "application/octet-stream",
".flr": "x-world/x-vrml",
".flv": "video/x-flv",
".fsscript": "application/fsharp-script",
".fsx": "application/fsharp-script",
".generictest": "application/xml",
".gif": "image/gif",
".group": "text/x-ms-group",
".gsm": "audio/x-gsm",
".gtar": "application/x-gtar",
".gz": "application/x-gzip",
".h": "text/plain",
".hdf": "application/x-hdf",
".hdml": "text/x-hdml",
".hhc": "application/x-oleobject",
".hhk": "application/octet-stream",
".hhp": "application/octet-stream",
".hlp": "application/winhlp",
".hpp": "text/plain",
".hqx": "application/mac-binhex40",
".hta": "application/hta",
".htc": "text/x-component",
".htm": "text/html",
".html": "text/html",
".htt": "text/webviewhtml",
".hxa": "application/xml",
".hxc": "application/xml",
".hxd": "application/octet-stream",
".hxe": "application/xml",
".hxf": "application/xml",
".hxh": "application/octet-stream",
".hxi": "application/octet-stream",
".hxk": "application/xml",
".hxq": "application/octet-stream",
".hxr": "application/octet-stream",
".hxs": "application/octet-stream",
".hxt": "text/html",
".hxv": "application/xml",
".hxw": "application/octet-stream",
".hxx": "text/plain",
".i": "text/plain",
".ico": "image/x-icon",
".ics": "application/octet-stream",
".idl": "text/plain",
".ief": "image/ief",
".iii": "application/x-iphone",
".inc": "text/plain",
".inf": "application/octet-stream",
".inl": "text/plain",
".ins": "application/x-internet-signup",
".ipa": "application/x-itunes-ipa",
".ipg": "application/x-itunes-ipg",
".ipproj": "text/plain",
".ipsw": "application/x-itunes-ipsw",
".iqy": "text/x-ms-iqy",
".isp": "application/x-internet-signup",
".ite": "application/x-itunes-ite",
".itlp": "application/x-itunes-itlp",
".itms": "application/x-itunes-itms",
".itpc": "application/x-itunes-itpc",
".IVF": "video/x-ivf",
".jar": "application/java-archive",
".java": "application/octet-stream",
".jck": "application/liquidmotion",
".jcz": "application/liquidmotion",
".jfif": "image/pjpeg",
".jnlp": "application/x-java-jnlp-file",
".jpb": "application/octet-stream",
".jpe": "image/jpeg",
".jpeg": "image/jpeg",
".jpg": "image/jpeg",
".js": "application/x-javascript",
".json": "application/json",
".jsx": "text/jscript",
".jsxbin": "text/plain",
".latex": "application/x-latex",
".library-ms": "application/windows-library+xml",
".lit": "application/x-ms-reader",
".loadtest": "application/xml",
".lpk": "application/octet-stream",
".lsf": "video/x-la-asf",
".lst": "text/plain",
".lsx": "video/x-la-asf",
".lzh": "application/octet-stream",
".m13": "application/x-msmediaview",
".m14": "application/x-msmediaview",
".m1v": "video/mpeg",
".m2t": "video/vnd.dlna.mpeg-tts",
".m2ts": "video/vnd.dlna.mpeg-tts",
".m2v": "video/mpeg",
".m3u": "audio/x-mpegurl",
".m3u8": "audio/x-mpegurl",
".m4a": "audio/m4a",
".m4b": "audio/m4b",
".m4p": "audio/m4p",
".m4r": "audio/x-m4r",
".m4v": "video/x-m4v",
".mac": "image/x-macpaint",
".mak": "text/plain",
".man": "application/x-troff-man",
".manifest": "application/x-ms-manifest",
".map": "text/plain",
".master": "application/xml",
".mda": "application/msaccess",
".mdb": "application/x-msaccess",
".mde": "application/msaccess",
".mdp": "application/octet-stream",
".me": "application/x-troff-me",
".mfp": "application/x-shockwave-flash",
".mht": "message/rfc822",
".mhtml": "message/rfc822",
".mid": "audio/mid",
".midi": "audio/mid",
".mix": "application/octet-stream",
".mk": "text/plain",
".mmf": "application/x-smaf",
".mno": "text/xml",
".mny": "application/x-msmoney",
".mod": "video/mpeg",
".mov": "video/quicktime",
".movie": "video/x-sgi-movie",
".mp2": "video/mpeg",
".mp2v": "video/mpeg",
".mp3": "audio/mpeg",
".mp4": "video/mp4",
".mp4v": "video/mp4",
".mpa": "video/mpeg",
".mpe": "video/mpeg",
".mpeg": "video/mpeg",
".mpf": "application/vnd.ms-mediapackage",
".mpg": "video/mpeg",
".mpp": "application/vnd.ms-project",
".mpv2": "video/mpeg",
".mqv": "video/quicktime",
".ms": "application/x-troff-ms",
".msi": "application/octet-stream",
".mso": "application/octet-stream",
".mts": "video/vnd.dlna.mpeg-tts",
".mtx": "application/xml",
".mvb": "application/x-msmediaview",
".mvc": "application/x-miva-compiled",
".mxp": "application/x-mmxp",
".nc": "application/x-netcdf",
".nsc": "video/x-ms-asf",
".nws": "message/rfc822",
".ocx": "application/octet-stream",
".oda": "application/oda",
".odc": "text/x-ms-odc",
".odh": "text/plain",
".odl": "text/plain",
".odp": "application/vnd.oasis.opendocument.presentation",
".ods": "application/oleobject",
".odt": "application/vnd.oasis.opendocument.text",
".one": "application/onenote",
".onea": "application/onenote",
".onepkg": "application/onenote",
".onetmp": "application/onenote",
".onetoc": "application/onenote",
".onetoc2": "application/onenote",
".orderedtest": "application/xml",
".osdx": "application/opensearchdescription+xml",
".p10": "application/pkcs10",
".p12": "application/x-pkcs12",
".p7b": "application/x-pkcs7-certificates",
".p7c": "application/pkcs7-mime",
".p7m": "application/pkcs7-mime",
".p7r": "application/x-pkcs7-certreqresp",
".p7s": "application/pkcs7-signature",
".pbm": "image/x-portable-bitmap",
".pcast": "application/x-podcast",
".pct": "image/pict",
".pcx": "application/octet-stream",
".pcz": "application/octet-stream",
".pdf": "application/pdf",
".pfb": "application/octet-stream",
".pfm": "application/octet-stream",
".pfx": "application/x-pkcs12",
".pgm": "image/x-portable-graymap",
".pic": "image/pict",
".pict": "image/pict",
".pkgdef": "text/plain",
".pkgundef": "text/plain",
".pko": "application/vnd.ms-pki.pko",
".pls": "audio/scpls",
".pma": "application/x-perfmon",
".pmc": "application/x-perfmon",
".pml": "application/x-perfmon",
".pmr": "application/x-perfmon",
".pmw": "application/x-perfmon",
".png": "image/png",
".pnm": "image/x-portable-anymap",
".pnt": "image/x-macpaint",
".pntg": "image/x-macpaint",
".pnz": "image/png",
".pot": "application/vnd.ms-powerpoint",
".potm": "application/vnd.ms-powerpoint.template.macroEnabled.12",
".potx": "application/vnd.openxmlformats-officedocument.presentationml.template",
".ppa": "application/vnd.ms-powerpoint",
".ppam": "application/vnd.ms-powerpoint.addin.macroEnabled.12",
".ppm": "image/x-portable-pixmap",
".pps": "application/vnd.ms-powerpoint",
".ppsm": "application/vnd.ms-powerpoint.slideshow.macroEnabled.12",
".ppsx": "application/vnd.openxmlformats-officedocument.presentationml.slideshow",
".ppt": "application/vnd.ms-powerpoint",
".pptm": "application/vnd.ms-powerpoint.presentation.macroEnabled.12",
".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
".prf": "application/pics-rules",
".prm": "application/octet-stream",
".prx": "application/octet-stream",
".ps": "application/postscript",
".psc1": "application/PowerShell",
".psd": "application/octet-stream",
".psess": "application/xml",
".psm": "application/octet-stream",
".psp": "application/octet-stream",
".pub": "application/x-mspublisher",
".pwz": "application/vnd.ms-powerpoint",
".qht": "text/x-html-insertion",
".qhtm": "text/x-html-insertion",
".qt": "video/quicktime",
".qti": "image/x-quicktime",
".qtif": "image/x-quicktime",
".qtl": "application/x-quicktimeplayer",
".qxd": "application/octet-stream",
".ra": "audio/x-pn-realaudio",
".ram": "audio/x-pn-realaudio",
".rar": "application/octet-stream",
".ras": "image/x-cmu-raster",
".rat": "application/rat-file",
".rc": "text/plain",
".rc2": "text/plain",
".rct": "text/plain",
".rdlc": "application/xml",
".resx": "application/xml",
".rf": "image/vnd.rn-realflash",
".rgb": "image/x-rgb",
".rgs": "text/plain",
".rm": "application/vnd.rn-realmedia",
".rmi": "audio/mid",
".rmp": "application/vnd.rn-rn_music_package",
".roff": "application/x-troff",
".rpm": "audio/x-pn-realaudio-plugin",
".rqy": "text/x-ms-rqy",
".rtf": "application/rtf",
".rtx": "text/richtext",
".ruleset": "application/xml",
".s": "text/plain",
".safariextz": "application/x-safari-safariextz",
".scd": "application/x-msschedule",
".sct": "text/scriptlet",
".sd2": "audio/x-sd2",
".sdp": "application/sdp",
".sea": "application/octet-stream",
".searchConnector-ms": "application/windows-search-connector+xml",
".setpay": "application/set-payment-initiation",
".setreg": "application/set-registration-initiation",
".settings": "application/xml",
".sgimb": "application/x-sgimb",
".sgml": "text/sgml",
".sh": "application/x-sh",
".shar": "application/x-shar",
".shtml": "text/html",
".sit": "application/x-stuffit",
".sitemap": "application/xml",
".skin": "application/xml",
".sldm": "application/vnd.ms-powerpoint.slide.macroEnabled.12",
".sldx": "application/vnd.openxmlformats-officedocument.presentationml.slide",
".slk": "application/vnd.ms-excel",
".sln": "text/plain",
".slupkg-ms": "application/x-ms-license",
".smd": "audio/x-smd",
".smi": "application/octet-stream",
".smx": "audio/x-smd",
".smz": "audio/x-smd",
".snd": "audio/basic",
".snippet": "application/xml",
".snp": "application/octet-stream",
".sol": "text/plain",
".sor": "text/plain",
".spc": "application/x-pkcs7-certificates",
".spl": "application/futuresplash",
".src": "application/x-wais-source",
".srf": "text/plain",
".SSISDeploymentManifest": "text/xml",
".ssm": "application/streamingmedia",
".sst": "application/vnd.ms-pki.certstore",
".stl": "application/vnd.ms-pki.stl",
".sv4cpio": "application/x-sv4cpio",
".sv4crc": "application/x-sv4crc",
".svc": "application/xml",
".swf": "application/x-shockwave-flash",
".t": "application/x-troff",
".tar": "application/x-tar",
".tcl": "application/x-tcl",
".testrunconfig": "application/xml",
".testsettings": "application/xml",
".tex": "application/x-tex",
".texi": "application/x-texinfo",
".texinfo": "application/x-texinfo",
".tgz": "application/x-compressed",
".thmx": "application/vnd.ms-officetheme",
".thn": "application/octet-stream",
".tif": "image/tiff",
".tiff": "image/tiff",
".tlh": "text/plain",
".tli": "text/plain",
".toc": "application/octet-stream",
".tr": "application/x-troff",
".trm": "application/x-msterminal",
".trx": "application/xml",
".ts": "video/vnd.dlna.mpeg-tts",
".tsv": "text/tab-separated-values",
".ttf": "application/octet-stream",
".tts": "video/vnd.dlna.mpeg-tts",
".txt": "text/plain",
".u32": "application/octet-stream",
".uls": "text/iuls",
".user": "text/plain",
".ustar": "application/x-ustar",
".vb": "text/plain",
".vbdproj": "text/plain",
".vbk": "video/mpeg",
".vbproj": "text/plain",
".vbs": "text/vbscript",
".vcf": "text/x-vcard",
".vcproj": "Application/xml",
".vcs": "text/plain",
".vcxproj": "Application/xml",
".vddproj": "text/plain",
".vdp": "text/plain",
".vdproj": "text/plain",
".vdx": "application/vnd.ms-visio.viewer",
".vml": "text/xml",
".vscontent": "application/xml",
".vsct": "text/xml",
".vsd": "application/vnd.visio",
".vsi": "application/ms-vsi",
".vsix": "application/vsix",
".vsixlangpack": "text/xml",
".vsixmanifest": "text/xml",
".vsmdi": "application/xml",
".vspscc": "text/plain",
".vss": "application/vnd.visio",
".vsscc": "text/plain",
".vssettings": "text/xml",
".vssscc": "text/plain",
".vst": "application/vnd.visio",
".vstemplate": "text/xml",
".vsto": "application/x-ms-vsto",
".vsw": "application/vnd.visio",
".vsx": "application/vnd.visio",
".vtx": "application/vnd.visio",
".wav": "audio/wav",
".wave": "audio/wav",
".wax": "audio/x-ms-wax",
".wbk": "application/msword",
".wbmp": "image/vnd.wap.wbmp",
".wcm": "application/vnd.ms-works",
".wdb": "application/vnd.ms-works",
".wdp": "image/vnd.ms-photo",
".webarchive": "application/x-safari-webarchive",
".webtest": "application/xml",
".wiq": "application/xml",
".wiz": "application/msword",
".wks": "application/vnd.ms-works",
".WLMP": "application/wlmoviemaker",
".wlpginstall": "application/x-wlpg-detect",
".wlpginstall3": "application/x-wlpg3-detect",
".wm": "video/x-ms-wm",
".wma": "audio/x-ms-wma",
".wmd": "application/x-ms-wmd",
".wmf": "application/x-msmetafile",
".wml": "text/vnd.wap.wml",
".wmlc": "application/vnd.wap.wmlc",
".wmls": "text/vnd.wap.wmlscript",
".wmlsc": "application/vnd.wap.wmlscriptc",
".wmp": "video/x-ms-wmp",
".wmv": "video/x-ms-wmv",
".wmx": "video/x-ms-wmx",
".wmz": "application/x-ms-wmz",
".wpl": "application/vnd.ms-wpl",
".wps": "application/vnd.ms-works",
".wri": "application/x-mswrite",
".wrl": "x-world/x-vrml",
".wrz": "x-world/x-vrml",
".wsc": "text/scriptlet",
".wsdl": "text/xml",
".wvx": "video/x-ms-wvx",
".x": "application/directx",
".xaf": "x-world/x-vrml",
".xaml": "application/xaml+xml",
".xap": "application/x-silverlight-app",
".xbap": "application/x-ms-xbap",
".xbm": "image/x-xbitmap",
".xdr": "text/plain",
".xht": "application/xhtml+xml",
".xhtml": "application/xhtml+xml",
".xla": "application/vnd.ms-excel",
".xlam": "application/vnd.ms-excel.addin.macroEnabled.12",
".xlc": "application/vnd.ms-excel",
".xld": "application/vnd.ms-excel",
".xlk": "application/vnd.ms-excel",
".xll": "application/vnd.ms-excel",
".xlm": "application/vnd.ms-excel",
".xls": "application/vnd.ms-excel",
".xlsb": "application/vnd.ms-excel.sheet.binary.macroEnabled.12",
".xlsm": "application/vnd.ms-excel.sheet.macroEnabled.12",
".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
".xlt": "application/vnd.ms-excel",
".xltm": "application/vnd.ms-excel.template.macroEnabled.12",
".xltx": "application/vnd.openxmlformats-officedocument.spreadsheetml.template",
".xlw": "application/vnd.ms-excel",
".xml": "text/xml",
".xmta": "application/xml",
".xof": "x-world/x-vrml",
".XOML": "text/plain",
".xpm": "image/x-xpixmap",
".xps": "application/vnd.ms-xpsdocument",
".xrm-ms": "text/xml",
".xsc": "application/xml",
".xsd": "text/xml",
".xsf": "text/xml",
".xsl": "text/xml",
".xslt": "text/xml",
".xsn": "application/octet-stream",
".xss": "application/xml",
".xtp": "application/octet-stream",
".xwd": "image/x-xwindowdump",
".z": "application/x-compress",
".zip": "application/x-zip-compressed"
}

【讨论】：

【解决方案9】：

此处介绍的两种解决方案的组合：

using System;
using System.Collections.Generic;

namespace Mime
{
    class Mime
    {

        public static string GetMimeType(string fileName)
        {
            if (string.IsNullOrEmpty(fileName) || string.IsNullOrWhiteSpace(fileName))
            {
                throw new ArgumentNullException("filename must contain a filename");
            }
            string extension = System.IO.Path.GetExtension(fileName).ToLower();

            if (!extension.StartsWith("."))
            {
                extension = "." + extension;
            }


            string mime;

            if (_mappings.TryGetValue(extension, out mime))
                return mime;
            if (GetWindowsMimeType(extension, out mime))
            {
                _mappings.Add(extension, mime);
                return mime;
            }
            return "application/octet-stream";
        }

        public static bool GetWindowsMimeType(string ext, out string mime)
        {
            mime="application/octet-stream";
            Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);

            if (regKey != null)
            { 
             object val=regKey.GetValue("Content Type") ;
             if (val != null)
             {
                 string strval = val.ToString();
                 if(!(string.IsNullOrEmpty(strval)||string.IsNullOrWhiteSpace(strval)))
                 {
                     mime=strval;
                     return true;
                 }
             }
            }
            return false;
        }

        static IDictionary<string, string> _mappings = new Dictionary<string, string>(StringComparer.InvariantCultureIgnoreCase) {

        #region Big freaking list of mime types
        // combination of values from Windows 7 Registry and 
        // from C:\Windows\System32\inetsrv\config\applicationHost.config
        // some added, including .7z and .dat
        {".323", "text/h323"},
        {".3g2", "video/3gpp2"},
        {".3gp", "video/3gpp"},
        {".3gp2", "video/3gpp2"},
        {".3gpp", "video/3gpp"},
        {".7z", "application/x-7z-compressed"},
        {".aa", "audio/audible"},
        {".AAC", "audio/aac"},
        {".aaf", "application/octet-stream"},
        {".aax", "audio/vnd.audible.aax"},
        {".ac3", "audio/ac3"},
        {".aca", "application/octet-stream"},
        {".accda", "application/msaccess.addin"},
        {".accdb", "application/msaccess"},
        {".accdc", "application/msaccess.cab"},
        {".accde", "application/msaccess"},
        {".accdr", "application/msaccess.runtime"},
        {".accdt", "application/msaccess"},
        {".accdw", "application/msaccess.webapplication"},
        {".accft", "application/msaccess.ftemplate"},
        {".acx", "application/internet-property-stream"},
        {".AddIn", "text/xml"},
        {".ade", "application/msaccess"},
        {".adobebridge", "application/x-bridge-url"},
        {".adp", "application/msaccess"},
        {".ADT", "audio/vnd.dlna.adts"},
        {".ADTS", "audio/aac"},
        {".afm", "application/octet-stream"},
        {".ai", "application/postscript"},
        {".aif", "audio/x-aiff"},
        {".aifc", "audio/aiff"},
        {".aiff", "audio/aiff"},
        {".air", "application/vnd.adobe.air-application-installer-package+zip"},
        {".amc", "application/x-mpeg"},
        {".application", "application/x-ms-application"},
        {".art", "image/x-jg"},
        {".asa", "application/xml"},
        {".asax", "application/xml"},
        {".ascx", "application/xml"},
        {".asd", "application/octet-stream"},
        {".asf", "video/x-ms-asf"},
        {".ashx", "application/xml"},
        {".asi", "application/octet-stream"},
        {".asm", "text/plain"},
        {".asmx", "application/xml"},
        {".aspx", "application/xml"},
        {".asr", "video/x-ms-asf"},
        {".asx", "video/x-ms-asf"},
        {".atom", "application/atom+xml"},
        {".au", "audio/basic"},
        {".avi", "video/x-msvideo"},
        {".axs", "application/olescript"},
        {".bas", "text/plain"},
        {".bcpio", "application/x-bcpio"},
        {".bin", "application/octet-stream"},
        {".bmp", "image/bmp"},
        {".c", "text/plain"},
        {".cab", "application/octet-stream"},
        {".caf", "audio/x-caf"},
        {".calx", "application/vnd.ms-office.calx"},
        {".cat", "application/vnd.ms-pki.seccat"},
        {".cc", "text/plain"},
        {".cd", "text/plain"},
        {".cdda", "audio/aiff"},
        {".cdf", "application/x-cdf"},
        {".cer", "application/x-x509-ca-cert"},
        {".chm", "application/octet-stream"},
        {".class", "application/x-java-applet"},
        {".clp", "application/x-msclip"},
        {".cmx", "image/x-cmx"},
        {".cnf", "text/plain"},
        {".cod", "image/cis-cod"},
        {".config", "application/xml"},
        {".contact", "text/x-ms-contact"},
        {".coverage", "application/xml"},
        {".cpio", "application/x-cpio"},
        {".cpp", "text/plain"},
        {".crd", "application/x-mscardfile"},
        {".crl", "application/pkix-crl"},
        {".crt", "application/x-x509-ca-cert"},
        {".cs", "text/plain"},
        {".csdproj", "text/plain"},
        {".csh", "application/x-csh"},
        {".csproj", "text/plain"},
        {".css", "text/css"},
        {".csv", "text/csv"},
        {".cur", "application/octet-stream"},
        {".cxx", "text/plain"},
        {".dat", "application/octet-stream"},
        {".datasource", "application/xml"},
        {".dbproj", "text/plain"},
        {".dcr", "application/x-director"},
        {".def", "text/plain"},
        {".deploy", "application/octet-stream"},
        {".der", "application/x-x509-ca-cert"},
        {".dgml", "application/xml"},
        {".dib", "image/bmp"},
        {".dif", "video/x-dv"},
        {".dir", "application/x-director"},
        {".disco", "text/xml"},
        {".dll", "application/x-msdownload"},
        {".dll.config", "text/xml"},
        {".dlm", "text/dlm"},
        {".doc", "application/msword"},
        {".docm", "application/vnd.ms-word.document.macroEnabled.12"},
        {".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
        {".dot", "application/msword"},
        {".dotm", "application/vnd.ms-word.template.macroEnabled.12"},
        {".dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"},
        {".dsp", "application/octet-stream"},
        {".dsw", "text/plain"},
        {".dtd", "text/xml"},
        {".dtsConfig", "text/xml"},
        {".dv", "video/x-dv"},
        {".dvi", "application/x-dvi"},
        {".dwf", "drawing/x-dwf"},
        {".dwp", "application/octet-stream"},
        {".dxr", "application/x-director"},
        {".eml", "message/rfc822"},
        {".emz", "application/octet-stream"},
        {".eot", "application/octet-stream"},
        {".eps", "application/postscript"},
        {".etl", "application/etl"},
        {".etx", "text/x-setext"},
        {".evy", "application/envoy"},
        {".exe", "application/octet-stream"},
        {".exe.config", "text/xml"},
        {".fdf", "application/vnd.fdf"},
        {".fif", "application/fractals"},
        {".filters", "Application/xml"},
        {".fla", "application/octet-stream"},
        {".flr", "x-world/x-vrml"},
        {".flv", "video/x-flv"},
        {".fsscript", "application/fsharp-script"},
        {".fsx", "application/fsharp-script"},
        {".generictest", "application/xml"},
        {".gif", "image/gif"},
        {".group", "text/x-ms-group"},
        {".gsm", "audio/x-gsm"},
        {".gtar", "application/x-gtar"},
        {".gz", "application/x-gzip"},
        {".h", "text/plain"},
        {".hdf", "application/x-hdf"},
        {".hdml", "text/x-hdml"},
        {".hhc", "application/x-oleobject"},
        {".hhk", "application/octet-stream"},
        {".hhp", "application/octet-stream"},
        {".hlp", "application/winhlp"},
        {".hpp", "text/plain"},
        {".hqx", "application/mac-binhex40"},
        {".hta", "application/hta"},
        {".htc", "text/x-component"},
        {".htm", "text/html"},
        {".html", "text/html"},
        {".htt", "text/webviewhtml"},
        {".hxa", "application/xml"},
        {".hxc", "application/xml"},
        {".hxd", "application/octet-stream"},
        {".hxe", "application/xml"},
        {".hxf", "application/xml"},
        {".hxh", "application/octet-stream"},
        {".hxi", "application/octet-stream"},
        {".hxk", "application/xml"},
        {".hxq", "application/octet-stream"},
        {".hxr", "application/octet-stream"},
        {".hxs", "application/octet-stream"},
        {".hxt", "text/html"},
        {".hxv", "application/xml"},
        {".hxw", "application/octet-stream"},
        {".hxx", "text/plain"},
        {".i", "text/plain"},
        {".ico", "image/x-icon"},
        {".ics", "application/octet-stream"},
        {".idl", "text/plain"},
        {".ief", "image/ief"},
        {".iii", "application/x-iphone"},
        {".inc", "text/plain"},
        {".inf", "application/octet-stream"},
        {".inl", "text/plain"},
        {".ins", "application/x-internet-signup"},
        {".ipa", "application/x-itunes-ipa"},
        {".ipg", "application/x-itunes-ipg"},
        {".ipproj", "text/plain"},
        {".ipsw", "application/x-itunes-ipsw"},
        {".iqy", "text/x-ms-iqy"},
        {".isp", "application/x-internet-signup"},
        {".ite", "application/x-itunes-ite"},
        {".itlp", "application/x-itunes-itlp"},
        {".itms", "application/x-itunes-itms"},
        {".itpc", "application/x-itunes-itpc"},
        {".IVF", "video/x-ivf"},
        {".jar", "application/java-archive"},
        {".java", "application/octet-stream"},
        {".jck", "application/liquidmotion"},
        {".jcz", "application/liquidmotion"},
        {".jfif", "image/pjpeg"},
        {".jnlp", "application/x-java-jnlp-file"},
        {".jpb", "application/octet-stream"},
        {".jpe", "image/jpeg"},
        {".jpeg", "image/jpeg"},
        {".jpg", "image/jpeg"},
        {".js", "application/x-javascript"},
        {".jsx", "text/jscript"},
        {".jsxbin", "text/plain"},
        {".latex", "application/x-latex"},
        {".library-ms", "application/windows-library+xml"},
        {".lit", "application/x-ms-reader"},
        {".loadtest", "application/xml"},
        {".lpk", "application/octet-stream"},
        {".lsf", "video/x-la-asf"},
        {".lst", "text/plain"},
        {".lsx", "video/x-la-asf"},
        {".lzh", "application/octet-stream"},
        {".m13", "application/x-msmediaview"},
        {".m14", "application/x-msmediaview"},
        {".m1v", "video/mpeg"},
        {".m2t", "video/vnd.dlna.mpeg-tts"},
        {".m2ts", "video/vnd.dlna.mpeg-tts"},
        {".m2v", "video/mpeg"},
        {".m3u", "audio/x-mpegurl"},
        {".m3u8", "audio/x-mpegurl"},
        {".m4a", "audio/m4a"},
        {".m4b", "audio/m4b"},
        {".m4p", "audio/m4p"},
        {".m4r", "audio/x-m4r"},
        {".m4v", "video/x-m4v"},
        {".mac", "image/x-macpaint"},
        {".mak", "text/plain"},
        {".man", "application/x-troff-man"},
        {".manifest", "application/x-ms-manifest"},
        {".map", "text/plain"},
        {".master", "application/xml"},
        {".mda", "application/msaccess"},
        {".mdb", "application/x-msaccess"},
        {".mde", "application/msaccess"},
        {".mdp", "application/octet-stream"},
        {".me", "application/x-troff-me"},
        {".mfp", "application/x-shockwave-flash"},
        {".mht", "message/rfc822"},
        {".mhtml", "message/rfc822"},
        {".mid", "audio/mid"},
        {".midi", "audio/mid"},
        {".mix", "application/octet-stream"},
        {".mk", "text/plain"},
        {".mmf", "application/x-smaf"},
        {".mno", "text/xml"},
        {".mny", "application/x-msmoney"},
        {".mod", "video/mpeg"},
        {".mov", "video/quicktime"},
        {".movie", "video/x-sgi-movie"},
        {".mp2", "video/mpeg"},
        {".mp2v", "video/mpeg"},
        {".mp3", "audio/mpeg"},
        {".mp4", "video/mp4"},
        {".mp4v", "video/mp4"},
        {".mpa", "video/mpeg"},
        {".mpe", "video/mpeg"},
        {".mpeg", "video/mpeg"},
        {".mpf", "application/vnd.ms-mediapackage"},
        {".mpg", "video/mpeg"},
        {".mpp", "application/vnd.ms-project"},
        {".mpv2", "video/mpeg"},
        {".mqv", "video/quicktime"},
        {".ms", "application/x-troff-ms"},
        {".msi", "application/octet-stream"},
        {".mso", "application/octet-stream"},
        {".mts", "video/vnd.dlna.mpeg-tts"},
        {".mtx", "application/xml"},
        {".mvb", "application/x-msmediaview"},
        {".mvc", "application/x-miva-compiled"},
        {".mxp", "application/x-mmxp"},
        {".nc", "application/x-netcdf"},
        {".nsc", "video/x-ms-asf"},
        {".nws", "message/rfc822"},
        {".ocx", "application/octet-stream"},
        {".oda", "application/oda"},
        {".odc", "text/x-ms-odc"},
        {".odh", "text/plain"},
        {".odl", "text/plain"},
        {".odp", "application/vnd.oasis.opendocument.presentation"},
        {".ods", "application/oleobject"},
        {".odt", "application/vnd.oasis.opendocument.text"},
        {".one", "application/onenote"},
        {".onea", "application/onenote"},
        {".onepkg", "application/onenote"},
        {".onetmp", "application/onenote"},
        {".onetoc", "application/onenote"},
        {".onetoc2", "application/onenote"},
        {".orderedtest", "application/xml"},
        {".osdx", "application/opensearchdescription+xml"},
        {".p10", "application/pkcs10"},
        {".p12", "application/x-pkcs12"},
        {".p7b", "application/x-pkcs7-certificates"},
        {".p7c", "application/pkcs7-mime"},
        {".p7m", "application/pkcs7-mime"},
        {".p7r", "application/x-pkcs7-certreqresp"},
        {".p7s", "application/pkcs7-signature"},
        {".pbm", "image/x-portable-bitmap"},
        {".pcast", "application/x-podcast"},
        {".pct", "image/pict"},
        {".pcx", "application/octet-stream"},
        {".pcz", "application/octet-stream"},
        {".pdf", "application/pdf"},
        {".pfb", "application/octet-stream"},
        {".pfm", "application/octet-stream"},
        {".pfx", "application/x-pkcs12"},
        {".pgm", "image/x-portable-graymap"},
        {".pic", "image/pict"},
        {".pict", "image/pict"},
        {".pkgdef", "text/plain"},
        {".pkgundef", "text/plain"},
        {".pko", "application/vnd.ms-pki.pko"},
        {".pls", "audio/scpls"},
        {".pma", "application/x-perfmon"},
        {".pmc", "application/x-perfmon"},
        {".pml", "application/x-perfmon"},
        {".pmr", "application/x-perfmon"},
        {".pmw", "application/x-perfmon"},
        {".png", "image/png"},
        {".pnm", "image/x-portable-anymap"},
        {".pnt", "image/x-macpaint"},
        {".pntg", "image/x-macpaint"},
        {".pnz", "image/png"},
        {".pot", "application/vnd.ms-powerpoint"},
        {".potm", "application/vnd.ms-powerpoint.template.macroEnabled.12"},
        {".potx", "application/vnd.openxmlformats-officedocument.presentationml.template"},
        {".ppa", "application/vnd.ms-powerpoint"},
        {".ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12"},
        {".ppm", "image/x-portable-pixmap"},
        {".pps", "application/vnd.ms-powerpoint"},
        {".ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12"},
        {".ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow"},
        {".ppt", "application/vnd.ms-powerpoint"},
        {".pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12"},
        {".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"},
        {".prf", "application/pics-rules"},
        {".prm", "application/octet-stream"},
        {".prx", "application/octet-stream"},
        {".ps", "application/postscript"},
        {".psc1", "application/PowerShell"},
        {".psd", "application/octet-stream"},
        {".psess", "application/xml"},
        {".psm", "application/octet-stream"},
        {".psp", "application/octet-stream"},
        {".pub", "application/x-mspublisher"},
        {".pwz", "application/vnd.ms-powerpoint"},
        {".qht", "text/x-html-insertion"},
        {".qhtm", "text/x-html-insertion"},
        {".qt", "video/quicktime"},
        {".qti", "image/x-quicktime"},
        {".qtif", "image/x-quicktime"},
        {".qtl", "application/x-quicktimeplayer"},
        {".qxd", "application/octet-stream"},
        {".ra", "audio/x-pn-realaudio"},
        {".ram", "audio/x-pn-realaudio"},
        {".rar", "application/octet-stream"},
        {".ras", "image/x-cmu-raster"},
        {".rat", "application/rat-file"},
        {".rc", "text/plain"},
        {".rc2", "text/plain"},
        {".rct", "text/plain"},
        {".rdlc", "application/xml"},
        {".resx", "application/xml"},
        {".rf", "image/vnd.rn-realflash"},
        {".rgb", "image/x-rgb"},
        {".rgs", "text/plain"},
        {".rm", "application/vnd.rn-realmedia"},
        {".rmi", "audio/mid"},
        {".rmp", "application/vnd.rn-rn_music_package"},
        {".roff", "application/x-troff"},
        {".rpm", "audio/x-pn-realaudio-plugin"},
        {".rqy", "text/x-ms-rqy"},
        {".rtf", "application/rtf"},
        {".rtx", "text/richtext"},
        {".ruleset", "application/xml"},
        {".s", "text/plain"},
        {".safariextz", "application/x-safari-safariextz"},
        {".scd", "application/x-msschedule"},
        {".sct", "text/scriptlet"},
        {".sd2", "audio/x-sd2"},
        {".sdp", "application/sdp"},
        {".sea", "application/octet-stream"},
        {".searchConnector-ms", "application/windows-search-connector+xml"},
        {".setpay", "application/set-payment-initiation"},
        {".setreg", "application/set-registration-initiation"},
        {".settings", "application/xml"},
        {".sgimb", "application/x-sgimb"},
        {".sgml", "text/sgml"},
        {".sh", "application/x-sh"},
        {".shar", "application/x-shar"},
        {".shtml", "text/html"},
        {".sit", "application/x-stuffit"},
        {".sitemap", "application/xml"},
        {".skin", "application/xml"},
        {".sldm", "application/vnd.ms-powerpoint.slide.macroEnabled.12"},
        {".sldx", "application/vnd.openxmlformats-officedocument.presentationml.slide"},
        {".slk", "application/vnd.ms-excel"},
        {".sln", "text/plain"},
        {".slupkg-ms", "application/x-ms-license"},
        {".smd", "audio/x-smd"},
        {".smi", "application/octet-stream"},
        {".smx", "audio/x-smd"},
        {".smz", "audio/x-smd"},
        {".snd", "audio/basic"},
        {".snippet", "application/xml"},
        {".snp", "application/octet-stream"},
        {".sol", "text/plain"},
        {".sor", "text/plain"},
        {".spc", "application/x-pkcs7-certificates"},
        {".spl", "application/futuresplash"},
        {".src", "application/x-wais-source"},
        {".srf", "text/plain"},
        {".SSISDeploymentManifest", "text/xml"},
        {".ssm", "application/streamingmedia"},
        {".sst", "application/vnd.ms-pki.certstore"},
        {".stl", "application/vnd.ms-pki.stl"},
        {".sv4cpio", "application/x-sv4cpio"},
        {".sv4crc", "application/x-sv4crc"},
        {".svc", "application/xml"},
        {".swf", "application/x-shockwave-flash"},
        {".t", "application/x-troff"},
        {".tar", "application/x-tar"},
        {".tcl", "application/x-tcl"},
        {".testrunconfig", "application/xml"},
        {".testsettings", "application/xml"},
        {".tex", "application/x-tex"},
        {".texi", "application/x-texinfo"},
        {".texinfo", "application/x-texinfo"},
        {".tgz", "application/x-compressed"},
        {".thmx", "application/vnd.ms-officetheme"},
        {".thn", "application/octet-stream"},
        {".tif", "image/tiff"},
        {".tiff", "image/tiff"},
        {".tlh", "text/plain"},
        {".tli", "text/plain"},
        {".toc", "application/octet-stream"},
        {".tr", "application/x-troff"},
        {".trm", "application/x-msterminal"},
        {".trx", "application/xml"},
        {".ts", "video/vnd.dlna.mpeg-tts"},
        {".tsv", "text/tab-separated-values"},
        {".ttf", "application/octet-stream"},
        {".tts", "video/vnd.dlna.mpeg-tts"},
        {".txt", "text/plain"},
        {".u32", "application/octet-stream"},
        {".uls", "text/iuls"},
        {".user", "text/plain"},
        {".ustar", "application/x-ustar"},
        {".vb", "text/plain"},
        {".vbdproj", "text/plain"},
        {".vbk", "video/mpeg"},
        {".vbproj", "text/plain"},
        {".vbs", "text/vbscript"},
        {".vcf", "text/x-vcard"},
        {".vcproj", "Application/xml"},
        {".vcs", "text/plain"},
        {".vcxproj", "Application/xml"},
        {".vddproj", "text/plain"},
        {".vdp", "text/plain"},
        {".vdproj", "text/plain"},
        {".vdx", "application/vnd.ms-visio.viewer"},
        {".vml", "text/xml"},
        {".vscontent", "application/xml"},
        {".vsct", "text/xml"},
        {".vsd", "application/vnd.visio"},
        {".vsi", "application/ms-vsi"},
        {".vsix", "application/vsix"},
        {".vsixlangpack", "text/xml"},
        {".vsixmanifest", "text/xml"},
        {".vsmdi", "application/xml"},
        {".vspscc", "text/plain"},
        {".vss", "application/vnd.visio"},
        {".vsscc", "text/plain"},
        {".vssettings", "text/xml"},
        {".vssscc", "text/plain"},
        {".vst", "application/vnd.visio"},
        {".vstemplate", "text/xml"},
        {".vsto", "application/x-ms-vsto"},
        {".vsw", "application/vnd.visio"},
        {".vsx", "application/vnd.visio"},
        {".vtx", "application/vnd.visio"},
        {".wav", "audio/wav"},
        {".wave", "audio/wav"},
        {".wax", "audio/x-ms-wax"},
        {".wbk", "application/msword"},
        {".wbmp", "image/vnd.wap.wbmp"},
        {".wcm", "application/vnd.ms-works"},
        {".wdb", "application/vnd.ms-works"},
        {".wdp", "image/vnd.ms-photo"},
        {".webarchive", "application/x-safari-webarchive"},
        {".webtest", "application/xml"},
        {".wiq", "application/xml"},
        {".wiz", "application/msword"},
        {".wks", "application/vnd.ms-works"},
        {".WLMP", "application/wlmoviemaker"},
        {".wlpginstall", "application/x-wlpg-detect"},
        {".wlpginstall3", "application/x-wlpg3-detect"},
        {".wm", "video/x-ms-wm"},
        {".wma", "audio/x-ms-wma"},
        {".wmd", "application/x-ms-wmd"},
        {".wmf", "application/x-msmetafile"},
        {".wml", "text/vnd.wap.wml"},
        {".wmlc", "application/vnd.wap.wmlc"},
        {".wmls", "text/vnd.wap.wmlscript"},
        {".wmlsc", "application/vnd.wap.wmlscriptc"},
        {".wmp", "video/x-ms-wmp"},
        {".wmv", "video/x-ms-wmv"},
        {".wmx", "video/x-ms-wmx"},
        {".wmz", "application/x-ms-wmz"},
        {".wpl", "application/vnd.ms-wpl"},
        {".wps", "application/vnd.ms-works"},
        {".wri", "application/x-mswrite"},
        {".wrl", "x-world/x-vrml"},
        {".wrz", "x-world/x-vrml"},
        {".wsc", "text/scriptlet"},
        {".wsdl", "text/xml"},
        {".wvx", "video/x-ms-wvx"},
        {".x", "application/directx"},
        {".xaf", "x-world/x-vrml"},
        {".xaml", "application/xaml+xml"},
        {".xap", "application/x-silverlight-app"},
        {".xbap", "application/x-ms-xbap"},
        {".xbm", "image/x-xbitmap"},
        {".xdr", "text/plain"},
        {".xht", "application/xhtml+xml"},
        {".xhtml", "application/xhtml+xml"},
        {".xla", "application/vnd.ms-excel"},
        {".xlam", "application/vnd.ms-excel.addin.macroEnabled.12"},
        {".xlc", "application/vnd.ms-excel"},
        {".xld", "application/vnd.ms-excel"},
        {".xlk", "application/vnd.ms-excel"},
        {".xll", "application/vnd.ms-excel"},
        {".xlm", "application/vnd.ms-excel"},
        {".xls", "application/vnd.ms-excel"},
        {".xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12"},
        {".xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12"},
        {".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
        {".xlt", "application/vnd.ms-excel"},
        {".xltm", "application/vnd.ms-excel.template.macroEnabled.12"},
        {".xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template"},
        {".xlw", "application/vnd.ms-excel"},
        {".xml", "text/xml"},
        {".xmta", "application/xml"},
        {".xof", "x-world/x-vrml"},
        {".XOML", "text/plain"},
        {".xpm", "image/x-xpixmap"},
        {".xps", "application/vnd.ms-xpsdocument"},
        {".xrm-ms", "text/xml"},
        {".xsc", "application/xml"},
        {".xsd", "text/xml"},
        {".xsf", "text/xml"},
        {".xsl", "text/xml"},
        {".xslt", "text/xml"},
        {".xsn", "application/octet-stream"},
        {".xss", "application/xml"},
        {".xtp", "application/octet-stream"},
        {".xwd", "image/x-xwindowdump"},
        {".z", "application/x-compress"},
        {".zip", "application/x-zip-compressed"},
        #endregion

        };

    }
}

【讨论】：

注册成功后，缓存到字典中

【解决方案10】：

为了使帖子更全面，对于 .NET Core 开发人员，有 FileExtensionContentTypeProvider 类，其中涵盖了官方的 MIME content types。

它在幕后工作 - 根据文件扩展名在 Http 响应标头中设置 ContentType。

如果您需要特殊的 MIME 类型，请参阅example on customising the MIME types：

public void Configure(IApplicationBuilder app)
{
    // Set up custom content types -associating file extension to MIME type
    var provider = new FileExtensionContentTypeProvider();
    // Add new mappings
    provider.Mappings[".myapp"] = "application/x-msdownload";
    provider.Mappings[".htm3"] = "text/html";
    provider.Mappings[".image"] = "image/png";
    // Replace an existing mapping
    provider.Mappings[".rtf"] = "application/x-msdownload";
    // Remove MP4 videos.
    provider.Mappings.Remove(".mp4");

    app.UseStaticFiles(new StaticFileOptions()
    {
        FileProvider = new PhysicalFileProvider(
            Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot", "images")),
        RequestPath = new PathString("/MyImages"),
        ContentTypeProvider = provider
    });

    app.UseDirectoryBrowser(new DirectoryBrowserOptions()
    {
        FileProvider = new PhysicalFileProvider(
            Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot", "images")),
        RequestPath = new PathString("/MyImages")
    });
}

【讨论】：

感谢您让我们知道这一点。给你一个提示：要获取 Web 应用程序的根文件夹，你应该使用 _hostingEnvironment.WebRootPath - 请参阅here

【解决方案11】：

大多数解决方案都有效，但为什么要如此努力，而我们也可以很容易地获得 mime 类型。在 System.Web 程序集中，有一种方法可以从文件名中获取 mime 类型。例如：

string mimeType = MimeMapping.GetMimeMapping(filename);

【讨论】：

3 年前在这一页上给出了相同的答案。 stackoverflow.com/a/14108040/315445

【解决方案12】：

使用 MimeTypeMap 包，它提供文件扩展名到 mime 类型和 mime 类型到文件扩展名的巨大双向映射

使用 MimeType；

将 mime 类型添加到扩展程序

Console.WriteLine("txt -> " + MimeTypeMap.GetMimeType("txt"));  // "text/plain"

获取 MIME 类型的扩展

Console.WriteLine("audio/wav -> " + MimeTypeMap.GetExtension("audio/wav")); // ".wav"

GitHub 网址：https://github.com/samuelneff/MimeTypeMap

【讨论】：

【解决方案13】：

受 Samuel 回答的启发，我写了一个改进版：

当扩展名是大写时也可以使用。
以文件名作为输入，优雅地处理无扩展名的文件。
不要包含“.”键。
来自Apache 的列表，我为此写了small transformation script。

生成的源代码超过 30K 个字符，因此我无法在此处发布，请查看on Github。

【讨论】：

【解决方案14】：

** 使用 MediaTypeNames 类-->示例：MediaTypeNames.Application.Pdf **

【讨论】：

虽然 MediaTypeNames 在使用 HttpResponseMessage 从 Web API 返回某些内容时会很方便，但它实际上与 OP 的要求相反。

【解决方案15】：

我对这些 mimetypes 的看法，使用 apache 列表，下面的脚本将为您提供一个包含所有 mimetypes 的字典。

var mimeTypeListUrl = "http://svn.apache.org/repos/asf/httpd/httpd/trunk/docs/conf/mime.types";
var webClient = new WebClient();
var rawData = webClient.DownloadString(mimeTypeListUrl).Split(new[] { Environment.NewLine, "\n" }, StringSplitOptions.RemoveEmptyEntries);

var extensionToMimeType = new Dictionary<string, string>();
var mimeTypeToExtension = new Dictionary<string, string[]>();

foreach (var row in rawData)
{
    if (row.StartsWith("#")) continue;

    var rowData = row.Split(new[] { "\t" }, StringSplitOptions.RemoveEmptyEntries);
    if (rowData.Length != 2) continue;

    var extensions = rowData[1].Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
    if (!mimeTypeToExtension.ContainsKey(rowData[0]))
    {
        mimeTypeToExtension.Add(rowData[0], extensions);
    }

    foreach (var extension in extensions)
    {
        if (!extensionToMimeType.ContainsKey(extension))
        {
            extensionToMimeType.Add(extension, rowData[0]);
        }
    }

}

【讨论】：

【解决方案16】：

您不应该相信来自客户端的文件扩展名。始终检查文件的幻数。

在 ASP.NET Core 中使用 FileTpeInterrogator：

public static class FileTypeChecker
{
    private static List<string> validVideoMimeTypes = new List<string> { "video/mp4", "video/quicktime" };
    private static List<string> validImageMimeTypes = new List<string> { "image/png", "image/jpeg" };

    public static bool IsValidVideo(IFormFile file)
    {
        return validVideoMimeTypes.Contains(GetFileMimeType(file));
    }

    public static bool IsValidImage(IFormFile file)
    {
        return validImageMimeTypes.Contains(GetFileMimeType(file));
    }

    private static string GetFileMimeType(IFormFile file)
    {
        // You should have checked for null and file length before reaching here

        IFileTypeInterrogator interrogator = new FileTypeInterrogator.FileTypeInterrogator();

        byte[] fileBytes;
        using (var stream = new MemoryStream())
        {
            file.CopyTo(stream);
            fileBytes = stream.ToArray();
        }

        FileTypeInfo fileTypeInfo = interrogator.DetectType(fileBytes);
        return fileTypeInfo.MimeType.ToLower();
    }
}

在您的控制器或服务内部：

public IActionResult UploadVideo([FromForm] UploadVideoVM model)
{
    if (model.File.Length < minimumLength || model.File.Length > maximumLength)
    {
        // BadRequest => Size
    }
    else if (!FileTypeChecker.IsValidVideo(model.File))
    {
        // BadRequest => Type
    }
    else
    {
        // All good
    }

    return Ok();
}

要获取文件扩展名的 MIME 类型，请参阅this file。

【讨论】：

存在与此 nuget 相关的漏洞问题：nvd.nist.gov/vuln/detail/CVE-2014-8117，还有其他选择吗？

【解决方案17】：

您可以使用Apache 的httpd 提供的表格。将其映射到函数、字典、列表等应该很简单。

另外，正如here 所见，extension->mime 类型不一定是函数。每个文件扩展名可能有多种常见的 MIME 类型，因此您应该查看应用程序的要求，并了解您为什么关心 MIME 类型、您想对它们“做什么”等。您可以使用文件扩展名来键入同样的行为？您是否还需要读取文件的前几个字节以确定其 MIME 类型？

【讨论】：

【解决方案18】：

这个帮助类返回任何文件名的 mime 类型（内容类型）、描述和图标：

using Microsoft.Win32;
using System;
using System.Drawing;
using System.IO;
using System.Runtime.InteropServices;

public static class Helper
{
    [DllImport("shell32.dll", CharSet = CharSet.Auto)]
    private static extern int ExtractIconEx(string lpszFile, int nIconIndex, IntPtr[] phIconLarge, IntPtr[] phIconSmall, int nIcons);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern int DestroyIcon(IntPtr hIcon);

    public static string GetFileContentType(string fileName)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        RegistryKey registryKey = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return string.Empty;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey == null)
            {
                return string.Empty;
            }

            object contentTypeObject = registryKey.GetValue("Content Type");
            if (!(contentTypeObject is string))
            {
                return string.Empty;
            }

            string contentType = (string)contentTypeObject;

            return contentType;
        }
        catch (Exception)
        {
            return null;
        }
        finally
        {
            if (registryKey != null)
            {
                registryKey.Close();
            }
        }
    }

    public static string GetFileDescription(string fileName)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        RegistryKey registryKey1 = null;
        RegistryKey registryKey2 = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return string.Empty;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey1 = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey1 == null)
            {
                return string.Empty;
            }

            object extensionDefaultObject = registryKey1.GetValue(null);
            if (!(extensionDefaultObject is string))
            {
                return string.Empty;
            }

            string extensionDefaultValue = (string)extensionDefaultObject;

            registryKey2 = Registry.ClassesRoot.OpenSubKey(extensionDefaultValue);
            if (registryKey2 == null)
            {
                return string.Empty;
            }

            object fileDescriptionObject = registryKey2.GetValue(null);
            if (!(fileDescriptionObject is string))
            {
                return string.Empty;
            }

            string fileDescription = (string)fileDescriptionObject;
            return fileDescription;
        }
        catch (Exception)
        {
            return null;
        }
        finally
        {
            if (registryKey2 != null)
            {
                registryKey2.Close();
            }

            if (registryKey1 != null)
            {
                registryKey1.Close();
            }
        }
    }

    public static void GetFileIcons(string fileName, out Icon smallIcon, out Icon largeIcon)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        smallIcon = null;
        largeIcon = null;

        RegistryKey registryKey1 = null;
        RegistryKey registryKey2 = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey1 = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey1 == null)
            {
                return;
            }

            object extensionDefaultObject = registryKey1.GetValue(null);
            if (!(extensionDefaultObject is string))
            {
                return;
            }

            string defaultIconKeyName = string.Format("{0}\\DefaultIcon", extensionDefaultObject);

            registryKey2 = Registry.ClassesRoot.OpenSubKey(defaultIconKeyName);
            if (registryKey2 == null)
            {
                return;
            }

            object defaultIconPathObject = registryKey2.GetValue(null);
            if (!(defaultIconPathObject is string))
            {
                return;
            }

            string defaultIconPath = (string)defaultIconPathObject;
            if (string.IsNullOrWhiteSpace(defaultIconPath))
            {
                return;
            }

            string iconfileName = null;
            int iconIndex = 0;

            int commaIndex = defaultIconPath.IndexOf(",");
            if (commaIndex > 0)
            {
                iconfileName = defaultIconPath.Substring(0, commaIndex);
                string iconIndexString = defaultIconPath.Substring(commaIndex + 1);

                if (!int.TryParse(iconIndexString, out iconIndex))
                {
                    iconIndex = 0;
                }
            }
            else
            {
                iconfileName = defaultIconPath;
                iconIndex = 0;
            }

            IntPtr[] phiconSmall = new IntPtr[1] { IntPtr.Zero };
            IntPtr[] phiconLarge = new IntPtr[1] { IntPtr.Zero };

            int readIconCount = ExtractIconEx(iconfileName, iconIndex, phiconLarge, phiconSmall, 1);

            if (readIconCount < 0)
            {
                return;
            }

            if (phiconSmall[0] != IntPtr.Zero)
            {
                smallIcon = (Icon)Icon.FromHandle(phiconSmall[0]).Clone();
                DestroyIcon(phiconSmall[0]);
            }

            if (phiconLarge[0] != IntPtr.Zero)
            {
                largeIcon = (Icon)Icon.FromHandle(phiconLarge[0]).Clone();
                DestroyIcon(phiconLarge[0]);
            }

            return;
        }
        finally
        {
            if (registryKey2 != null)
            {
                registryKey2.Close();
            }

            if (registryKey1 != null)
            {
                registryKey1.Close();
            }
        }
    }
}

用法：

string fileName = "NotExists.txt";
string contentType = Helper.GetFileContentType(fileName); // "text/plain"
string description = Helper.GetFileDescription(fileName); // "Text Document"
Icon smallIcon, largeIcon;
Helper.GetFileIcons(fileName, out smallIcon, out largeIcon); // 16x16, 32x32 icons

【讨论】：

不幸的是，这不能跨平台工作，并且由于它使用 RegistryKeys 很容易在云中造成麻烦

【解决方案19】：

如果您不想添加额外的依赖项并且仍然想要与版本无关的请求，您可以将this answer on how to get the MIME-Type in different .NET versions 与this answer on conditional builds for multiple .NET Framework versions 混合使用。

我做的第一件事是编辑我的项目文件。在最后一个构建定义之后，我添加了第二个答案中所述的属性组：

<PropertyGroup>
    <DefineConstants Condition=" !$(DefineConstants.Contains(';NET')) ">$(DefineConstants);$(TargetFrameworkVersion.Replace("v", "NET").Replace(".", ""))</DefineConstants>
    <DefineConstants Condition=" $(DefineConstants.Contains(';NET')) ">$(DefineConstants.Remove($(DefineConstants.LastIndexOf(";NET"))));$(TargetFrameworkVersion.Replace("v", "NET").Replace(".", ""))</DefineConstants>
</PropertyGroup>

现在，我为第一个答案中的 MimeExtensionHelper 提供了不同的实现，并为来自 .NET 4.5 或更高版本的所有客户端提供了一个额外的实现，只需调用 System.Web.MimeMapping.GetMimeMapping：

#if (NET10 || NET11 || NET20 || NET30 || NET35)
public static class MimeExtensionHelper
{
    static object locker = new object();
    static MethodInfo getMimeMappingMethodInfo;

    static MimeExtensionHelper()
    {
        Type mimeMappingType = Assembly.GetAssembly(typeof(HttpRuntime)).GetType("System.Web.MimeMapping");

        if (mimeMappingType == null)
            throw new SystemException("Couldnt find MimeMapping type");

        ConstructorInfo constructorInfo = mimeMappingType.GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance, null, Type.EmptyTypes, null);

        if (constructorInfo == null)
            throw new SystemException("Couldnt find default constructor for MimeMapping");

        mimeMapping = constructorInfo.Invoke(null);

        if (mimeMapping == null)
            throw new SystemException("Couldnt find MimeMapping");

        getMimeMappingMethodInfo = mimeMappingType.GetMethod("GetMimeMapping", BindingFlags.Static | BindingFlags.NonPublic);

        if (getMimeMappingMethodInfo == null)
            throw new SystemException("Couldnt find GetMimeMapping method");

        if (getMimeMappingMethodInfo.ReturnType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid return type");

        if (getMimeMappingMethodInfo.GetParameters().Length != 1 && getMimeMappingMethodInfo.GetParameters()[0].ParameterType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid parameters");
    }

    public static string GetMimeType(string fileName)
    {
        lock (locker)
        {
            return (string)getMimeMappingMethodInfo.Invoke(null, new object[] { fileName });
        }
    }
}
#elif NET40
public static class MimeExtensionHelper
{
    static object locker = new object();
    static MethodInfo getMimeMappingMethodInfo;

    static MimeExtensionHelper()
    {
        Type mimeMappingType = Assembly.GetAssembly(typeof(HttpRuntime)).GetType("System.Web.MimeMapping");

        if (mimeMappingType == null)
            throw new SystemException("Couldnt find MimeMapping type");           

        getMimeMappingMethodInfo = mimeMappingType.GetMethod("GetMimeMapping", BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public);

        if (getMimeMappingMethodInfo == null)
            throw new SystemException("Couldnt find GetMimeMapping method");

        if (getMimeMappingMethodInfo.ReturnType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid return type");

        if (getMimeMappingMethodInfo.GetParameters().Length != 1 && getMimeMappingMethodInfo.GetParameters()[0].ParameterType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid parameters");
    }

    public static string GetMimeType(string fileName)
    {
        lock (locker)
        {
            return (string)getMimeMappingMethodInfo.Invoke(null, new object[] { fileName });
        }
    }
}
#else // .NET 4.5 or later
public static class MimeExtensionHelper
{
    public static string GetMimeType(string fileName)
    {
        return MimeMapping.GetMimeMapping(fileName);
    }
}
#endif

同样在 .NET 4.5 之前的版本中，静态 MimeMapping 类托管一个名为 _mappingDictionary（类型为 MimeMapping.MimeMappingDictionaryBase）的静态实例，您可以从 Reflection 请求该实例以添加新的 MIME 类型，这可能尚不支持。

【讨论】：

【解决方案20】：

通过文件扩展计算的mime类型不一定总是正确的。

假设我可以保存扩展名为 .png 的文件，但文件格式可以设置为“ImageFormat.jpeg”。

所以在这种情况下，您将要计算的文件会给出不同的结果...它可能会导致文件比原始文件大。

如果您正在处理图像，则可以使用 imagecodecInfo 和 ImageFormat。

【讨论】：

【解决方案21】：

Bryan Denny 上面的帖子对我不起作用，因为并非所有扩展在注册表中都有“内容类型”子键。我不得不按如下方式调整代码：

private string GetMimeType(string sFileName)
{
  // Get file extension and if it is empty, return unknown
  string sExt = Path.GetExtension(sFileName);
  if (string.IsNullOrEmpty(sExt)) return "Unknown file type";

  // Default type is "EXT File"
  string mimeType = string.Format("{0} File", sExt.ToUpper().Replace(".", ""));

  // Open the registry key for the extension under HKEY_CLASSES_ROOT and return default if it doesn't exist
  Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(sExt);
  if (regKey == null) return mimeType;

  // Get the "(Default)" value and re-open the key for that value
  string sSubType = regKey.GetValue("").ToString();
  regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(sSubType);

  // If it exists, get the "(Default)" value of the new key
  if (regKey?.GetValue("") != null) mimeType = regKey.GetValue("").ToString();

  // Return the value
  return mimeType;
}

现在它适用于所有已注册文件类型和未注册或通用文件类型（如 JPG 等）。

【讨论】：

【解决方案22】：

我已经为 mime 类型和内容类型值编制了一个信誉良好的来源列表，这些值仅以文件扩展名为键（当前）。

nuget 包在这里https://www.nuget.org/packages/FTTLib.dll/

来源在这里https://github.com/brondavies/filetypetranslator/

这个库的设计目的是：

无外部依赖项
没有文件系统访问权限
内存占用小
简单的静态方法（没有扩展方法和可实例化的类）
不区分大小写
便携式 - 适用于针对任何 CLR (.NET 2.0+) 的应用程序

【讨论】：

【解决方案23】：

当然，为了将共同的完整性、动态性和可移植性的优势与最小的依赖相结合

您会将 Samuel Neff 的静态字典与特定于平台的查询结合起来，例如布莱恩·丹尼（Bryan Denny）。

例如Linux 下的命令行工具“xdg-mime”可能会做后面的部分。

【讨论】：

【解决方案24】：

如果有人可以在 linux 上使用与 libmagic 中类似的功能会更好，因为我认为这是检测文件类型的更好方法，而不是中继文件的扩展名。

例如，如果我将文件从 mypicture.jpg 重命名为 mypicture.txt 在linux上，还是会报图片的但是在这里使用这种方法，它将被报告为文本文件。

问候托马斯

【讨论】：

【解决方案25】：

IANA 媒体类型

我希望微软能够一起制定他们的行业标准法案！对于其他人，任何感兴趣的人：

离散类型

多部分类型

我想向有兴趣的人推荐阅读：MIME types (IANA media types) Mozilla 页面！内容非常丰富！

代码方面，上述每个链接都有一个 .csv 文件下载：https://www.iana.org/assignments/media-types/application.csv

正如这里已经指出的，字典或 ConcurrentDictionary 可能是下载并使用键值对填充字典的想法。

【讨论】：

【解决方案26】：

FileExtension 处理文件扩展名而不是 Mime。用户可以更改文件扩展名，因此请检查 Mime。代码示例通过文件扩展名关联 Mime，这是错误的，不起作用。

需要获取contenttype文件并根据文件扩展名检查表是否Mime contetType这个文件。现在，如何获取文件的ContentType？

因此使用 FileUpload 是：FileUpload.PostedFile.ContentType; 现在，如果我已经有文件，是否捕获了您的 ContentType？

【讨论】：

【解决方案27】：

您可以使用 MimeMappings 类。我认为这是最简单的方法。我也导入了 MimeMappings。因为我觉得找到这些类的导入很麻烦。

import org.springframework.boot.web.server.MimeMappings;    
MimeMappings mm=new MimeMappings();
String mimetype = mm.get(fileExtension);
System.out.println(mimetype);

【讨论】：