默认 HTTP 标头是否有任何常量？

Question

Microsoft 是否为标准 HTTP 标头名称创建了一个充满常量的类，还是我必须自己编写？

Answer 1

请求标头

/// <summary>
/// Contains the standard set of headers applicable to an HTTP request.
/// </summary>
public static class HttpRequestHeaders
{
    ///<summary>Content-Types that are acceptable</summary>
    public const string Accept = "Accept";
    ///<summary>Character sets that are acceptable</summary>
    public const string AcceptCharset = "Accept-Charset";
    ///<summary>Acceptable encodings. See HTTP compression.</summary>
    public const string AcceptEncoding = "Accept-Encoding";
    ///<summary>Acceptable languages for response</summary>
    public const string AcceptLanguage = "Accept-Language";
    ///<summary>Acceptable version in time</summary>
    public const string AcceptDatetime = "Accept-Datetime";
    ///<summary>Authentication credentials for HTTP authentication</summary>
    public const string Authorization = "Authorization";
    ///<summary>Used to specify directives that MUST be obeyed by all caching mechanisms along the request/response chain</summary>
    public const string CacheControl = "Cache-Control";
    ///<summary>What type of connection the user-agent would prefer</summary>
    public const string Connection = "Connection";
    ///<summary>an HTTP cookie previously sent by the server with Set-Cookie (below)</summary>
    public const string Cookie = "Cookie";
    ///<summary>The length of the request body in octets (8-bit bytes)</summary>
    public const string ContentLength = "Content-Length";
    ///<summary>A Base64-encoded binary MD5 sum of the content of the request body</summary>
    public const string ContentMD5 = "Content-MD5";
    ///<summary>The MIME type of the body of the request (used with POST and PUT requests)</summary>
    public const string ContentType = "Content-Type";
    ///<summary>The date and time that the message was sent</summary>
    public const string Date = "Date";
    ///<summary>Indicates that particular server behaviors are required by the client</summary>
    public const string Expect = "Expect";
    ///<summary>The email address of the user making the request</summary>
    public const string From = "From";
    ///<summary>The domain name of the server (for virtual hosting), mandatory since HTTP/1.1. Although domain name are specified as case-insensitive[5][6], it is not specified whether the contents of the Host field should be interpreted in a case-insensitive manner[7] and in practice some implementations of virtual hosting interpret the contents of the Host field in a case-sensitive manner.[citation needed]</summary>
    public const string Host = "Host";
    ///<summary>Only perform the action if the client supplied entity matches the same entity on the server. This is mainly for methods like PUT to only update a resource if it has not been modified since the user last updated it.</summary>
    public const string IfMatch = "If-Match";
    ///<summary>Allows a 304 Not Modified to be returned if content is unchanged</summary>
    public const string IfModifiedSince = "If-Modified-Since";
    ///<summary>Allows a 304 Not Modified to be returned if content is unchanged, see HTTP ETag</summary>
    public const string IfNoneMatch = "If-None-Match";
    ///<summary>If the entity is unchanged, send me the part(s) that I am missing; otherwise, send me the entire new entity</summary>
    public const string IfRange = "If-Range";
    ///<summary>Only send the response if the entity has not been modified since a specific time.</summary>
    public const string IfUnmodifiedSince = "If-Unmodified-Since";
    ///<summary>Limit the number of times the message can be forwarded through proxies or gateways.</summary>
    public const string MaxForwards = "Max-Forwards";
    ///<summary>Implementation-specific headers that may have various effects anywhere along the request-response chain.</summary>
    public const string Pragma = "Pragma";
    ///<summary>Authorization credentials for connecting to a proxy.</summary>
    public const string ProxyAuthorization = "Proxy-Authorization";
    ///<summary>Request only part of an entity. Bytes are numbered from 0.</summary>
    public const string Range = "Range";
    ///<summary>This is the address of the previous web page from which a link to the currently requested page was followed. (The word “referrer” is misspelled in the RFC as well as in most implementations.)</summary>
    public const string Referersic = "Referer[sic]";
    ///<summary>The transfer encodings the user agent is willing to accept: the same values as for the response header Transfer-Encoding can be used, plus the trailers value (related to the chunked transfer method) to notify the server it expects to receive additional headers (the trailers) after the last, zero-sized, chunk.</summary>
    public const string TE = "TE";
    ///<summary>Ask the server to upgrade to another protocol.</summary>
    public const string Upgrade = "Upgrade";
    ///<summary>The user agent string of the user agent</summary>
    public const string UserAgent = "User-Agent";
    ///<summary>Informs the server of proxies through which the request was sent.</summary>
    public const string Via = "Via";
    ///<summary>A general warning about possible problems with the entity body.</summary>
    public const string Warning = "Warning";
    ///<summary>Contains the original source address of the request.</summary>
    public const string XForwardedFor = "X-Forwarded-For";
}

响应标头

/// <summary>
/// Contains the standard set of headers applicable to an HTTP response.
/// </summary>
public static class HttpResponseHeaders
{
    ///<summary>What partial content range types this server supports</summary>
    public const string AcceptRanges = "Accept-Ranges";
    ///<summary>The age the object has been in a proxy cache in seconds</summary>
    public const string Age = "Age";
    ///<summary>Valid actions for a specified resource. To be used for a 405 Method not allowed</summary>
    public const string Allow = "Allow";
    ///<summary>Tells all caching mechanisms from server to client whether they may cache this object. It is measured in seconds</summary>
    public const string CacheControl = "Cache-Control";
    ///<summary>Options that are desired for the connection[17]</summary>
    public const string Connection = "Connection";
    ///<summary>The type of encoding used on the data. See HTTP compression.</summary>
    public const string ContentEncoding = "Content-Encoding";
    ///<summary>The language the content is in</summary>
    public const string ContentLanguage = "Content-Language";
    ///<summary>The length of the response body in octets (8-bit bytes)</summary>
    public const string ContentLength = "Content-Length";
    ///<summary>An alternate location for the returned data</summary>
    public const string ContentLocation = "Content-Location";
    ///<summary>A Base64-encoded binary MD5 sum of the content of the response</summary>
    public const string ContentMD5 = "Content-MD5";
    ///<summary>An opportunity to raise a File Download dialogue box for a known MIME type with binary format or suggest a filename for dynamic content. Quotes are necessary with special characters.</summary>
    public const string ContentDisposition = "Content-Disposition";
    ///<summary>Where in a full body message this partial message belongs</summary>
    public const string ContentRange = "Content-Range";
    ///<summary>The MIME type of this content</summary>
    public const string ContentType = "Content-Type";
    ///<summary>The date and time that the message was sent</summary>
    public const string Date = "Date";
    ///<summary>An identifier for a specific version of a resource, often a message digest</summary>
    public const string ETag = "ETag";
    ///<summary>Gives the date/time after which the response is considered stale</summary>
    public const string Expires = "Expires";
    ///<summary>The last modified date for the requested object, inRFC 2822 format</summary>
    public const string LastModified = "Last-Modified";
    ///<summary>Used to express a typed relationship with another resource, where the relation type is defined by RFC 5988</summary>
    public const string Link = "Link";
    ///<summary>Used in redirection, or when a new resource has been created.</summary>
    public const string Location = "Location";
    ///<summary>This header is supposed to set P3P policy, in the form of P3P:CP=your_compact_policy. However, P3P did not take off,[22] most browsers have never fully implemented it, a lot of websites set this header with fake policy text, that was enough to fool browsers the existence of P3P policy and grant permissions for third party cookies.</summary>
    public const string P3P = "P3P";
    ///<summary>Implementation-specific headers that may have various effects anywhere along the request-response chain.</summary>
    public const string Pragma = "Pragma";
    ///<summary>Request authentication to access the proxy.</summary>
    public const string ProxyAuthenticate = "Proxy-Authenticate";
    ///<summary>Used in redirection, or when a new resource has been created. This refresh redirects after 5 seconds. This is a proprietary, non-standard header extension introduced by Netscape and supported by most web browsers.</summary>
    public const string Refresh = "Refresh";
    ///<summary>If an entity is temporarily unavailable, this instructs the client to try again after a specified period of time (seconds).</summary>
    public const string RetryAfter = "Retry-After";
    ///<summary>A name for the server</summary>
    public const string Server = "Server";
    ///<summary>an HTTP cookie</summary>
    public const string SetCookie = "Set-Cookie";
    ///<summary>A HSTS Policy informing the HTTP client how long to cache the HTTPS only policy and whether this applies to subdomains.</summary>
    public const string StrictTransportSecurity = "Strict-Transport-Security";
    ///<summary>The Trailer general field value indicates that the given set of header fields is present in the trailer of a message encoded with chunked transfer-coding.</summary>
    public const string Trailer = "Trailer";
    ///<summary>The form of encoding used to safely transfer the entity to the user. Currently defined methods are:chunked, compress, deflate, gzip, identity.</summary>
    public const string TransferEncoding = "Transfer-Encoding";
    ///<summary>Tells downstream proxies how to match future request headers to decide whether the cached response can be used rather than requesting a fresh one from the origin server.</summary>
    public const string Vary = "Vary";
    ///<summary>Informs the client of proxies through which the response was sent.</summary>
    public const string Via = "Via";
    ///<summary>A general warning about possible problems with the entity body.</summary>
    public const string Warning = "Warning";
    ///<summary>Indicates the authentication scheme that should be used to access the requested entity.</summary>
    public const string WWWAuthenticate = "WWW-Authenticate";       
}

Answer 2

Microsoft 为请求和响应标头创建了枚举。

看看以下内容：

HttpResponseHeader

HttpRequestHeader

Answer 3

扩展 Jed 的答案。

HttpResponseHeader 和HttpRequestHeader 枚举可以用作使用WebHeaderCollection 时的常量。 WebHeaderCollection 包含接受这些枚举的索引器属性。

您可以使用字符串或枚举之一来获取和设置标头值，并在您的代码中混合使用。

示例 LinqPad 脚本：

var headers = new WebHeaderCollection();

headers["If-Modified-Since"] = "Sat, 29 Oct 1994 19:43:31 GMT"; 
// shows header name as "If-Modified-Since"
headers.Dump();
// shows expected header value of "Sat, 29 Oct 1994 19:43:31 GMT"
headers[HttpRequestHeader.IfModifiedSince].Dump();

headers.Clear();

headers[HttpRequestHeader.IfModifiedSince] = "Sat, 29 Oct 1994 19:43:31 GMT";
// shows header name as "If-Modified-Since"
headers.Dump(); 
// shows expected header value "Sat, 29 Oct 1994 19:43:31 GMT"
headers["If-Modified-Since"].Dump();

Answer 4

他们在HttpKnownHeaderNames 中有它们，但不幸的是该类是内部的。我为它开了一个问题：https://github.com/dotnet/corefx/issues/10632。

Answer 5

我在尝试发现同一件事时发现了这个问题：标题名称常量作为字符串在哪里？

在 ASP.NET Core 中，Microsoft.Net.Http.Headers.HeaderNames 是拯救我的类。

public static class HeaderNames
  {
    public const string Accept = "Accept";
    public const string AcceptCharset = "Accept-Charset";
    public const string AcceptEncoding = "Accept-Encoding";
    public const string AcceptLanguage = "Accept-Language";
    public const string AcceptRanges = "Accept-Ranges";
    public const string Age = "Age";
    public const string Allow = "Allow";
    public const string Authorization = "Authorization";
    public const string CacheControl = "Cache-Control";
    public const string Connection = "Connection";
    public const string ContentDisposition = "Content-Disposition";
    public const string ContentEncoding = "Content-Encoding";
    public const string ContentLanguage = "Content-Language";
    public const string ContentLength = "Content-Length";
    public const string ContentLocation = "Content-Location";
    public const string ContentMD5 = "Content-MD5";
    public const string ContentRange = "Content-Range";
    public const string ContentType = "Content-Type";
    public const string Cookie = "Cookie";
    public const string Date = "Date";
    public const string ETag = "ETag";
    public const string Expires = "Expires";
    public const string Expect = "Expect";
    public const string From = "From";
    public const string Host = "Host";
    public const string IfMatch = "If-Match";
    public const string IfModifiedSince = "If-Modified-Since";
    public const string IfNoneMatch = "If-None-Match";
    public const string IfRange = "If-Range";
    public const string IfUnmodifiedSince = "If-Unmodified-Since";
    public const string LastModified = "Last-Modified";
    public const string Location = "Location";
    public const string MaxForwards = "Max-Forwards";
    public const string Pragma = "Pragma";
    public const string ProxyAuthenticate = "Proxy-Authenticate";
    public const string ProxyAuthorization = "Proxy-Authorization";
    public const string Range = "Range";
    public const string Referer = "Referer";
    public const string RetryAfter = "Retry-After";
    public const string Server = "Server";
    public const string SetCookie = "Set-Cookie";
    public const string TE = "TE";
    public const string Trailer = "Trailer";
    public const string TransferEncoding = "Transfer-Encoding";
    public const string Upgrade = "Upgrade";
    public const string UserAgent = "User-Agent";
    public const string Vary = "Vary";
    public const string Via = "Via";
    public const string Warning = "Warning";
    public const string WebSocketSubProtocols = "Sec-WebSocket-Protocol";
    public const string WWWAuthenticate = "WWW-Authenticate";
  }

Answer 6

using System.Net.HttpRequestHeader;
using System.Net.HttpResponseHeader;

public class Example {
  static void Main() {
    Console.WriteLine(HttpRequestHeader.IfModifiedSince.ToHeaderString());
    // If-Modified-Since

    Console.WriteLine(HttpResponseHeader.ContentLength.ToHeaderString());
    // Content-Length
  }
}

static class ExtensionMethods {
  public static string ToHeaderString(this HttpRequestHeader instance)
  {
    return Regex.Replace(instance.ToString(), "(\\B[A-Z])", "-$1");
  }

  public static string ToHeaderString(this HttpResponseHeader instance)
  {
    return Regex.Replace(instance.ToString(), "(\\B[A-Z])", "-$1");
  }
}

Answer 7

Microsoft.Net.Http.Headers nuget 包中有一些可用的。在我的 asp.net 核心项目中它已经安装了。

示例用法：

var value = request.Headers[Microsoft.Net.Http.Headers.HeaderNames.IfNoneMatch]

可能是某些人正在寻找的东西？

Answer 8

如果您使用的是 .NET Framework（不是 .NET Core），您可以创建一个扩展方法来正确格式化 System.Net.HttpRequestHeader 枚举：

using System;
using System.Net;
using System.Text;

namespace YourNamespace
{
   public static class HttpRequestHeaderEx
   {
      public static string ToStandardName(this HttpRequestHeader requestHeader)
      {
         string headerName = requestHeader.ToString();

         var headerStandardNameBuilder = new StringBuilder();
         headerStandardNameBuilder.Append(headerName[0]);

         for (int index = 1; index < headerName.Length; index++)
         {
            char character = headerName[index];
            if (char.IsUpper(character))
            {
               headerStandardNameBuilder.Append('-');
            }

            headerStandardNameBuilder.Append(character);
         }

         string headerStandardName = headerStandardNameBuilder.ToString();

         return headerStandardName;
      }
   }
}

用法：

   var userAgentHeaderName = HttpRequestHeader.UserAgent.ToStandardName();

Answer 9

Microsoft.Net.Http.Headers.HeaderNames 类曾经是最好的，开箱即用的选项。

但是从 ASP.NET Core 3.0 开始，该类具有静态只读字段而不是常量。原因是performance optimization of comparisons：

1. 引用比较比字符串内容顺序不区分大小写比较快。
2. 常量成为消费程序集的一部分，而静态字段则不会。因此，在不同程序集中对常量的使用之间的引用过去是不同的，而在更改后，它们都是相同的。

这种优化的缺点是“常量”不再是编译时常量，因此无法使用，例如带有属性 ([FromHeader(Name = HeaderNames.IfNoneMatch)])。

只需在代码中创建您自己的类副本，使用实际常量而不是静态字段。