如何使用 webclient 调用 web api 将文档下载到网站目录

Question

我正在努力使用基于从 WebAPI 返回的字节数组的数据创建文件。以下是我调用 web api 的代码

 using (var http = new WebClient())
            {
                string url = string.Format("{0}api/FileUpload/FileServe?FileID=" + fileID, webApiUrl);
                http.Headers[HttpRequestHeader.ContentType] = "application/octet-stream";
                http.Headers[HttpRequestHeader.Authorization] = "Bearer " + authCookie.Value;
                http.DownloadDataCompleted += Http_DownloadDataCompleted;
                byte[] json = await http.DownloadDataTaskAsync(url);



            }

api代码是

[HttpGet]
    [Route("FileServe")]
    [Authorize(Roles = "Admin,SuperAdmin,Contractor")]
    public async Task<HttpResponseMessage> GetFile(int FileID)
    {
        using (var repo = new MBHDocRepository())
        {
            var file = await repo.GetSpecificFile(FileID);
            if (file == null)
            {
                throw new HttpResponseException(HttpStatusCode.BadRequest);
            }

            var stream = File.Open(file.PathLocator, FileMode.Open);
            HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
            response.Content = new StreamContent(stream);
            response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(file.FileType);
            return response;
        }
    }

我收到一个字节数组作为响应，但是我无法从该字节数组创建相应的文件。我不知道如何将字节数组转换为相关的文件类型（例如 jpg 或基于 web api 中文件类型的 pdf）。任何帮助将不胜感激。

Answer 1

好的，首先有几种方法可以解决您的问题，在服务器端，您可以简单地发送内容类型并将其保留，或者您也可以发送完整的文件名，这会进一步帮助您。

我已使用基本测试代码删除了特定于您的内容的代码，请忽略这些内容并根据您的代码使用它。

这里有一些设计说明：

            [HttpGet]
            [Route("FileServe")]
            [Authorize(Roles = "Admin,SuperAdmin,Contractor")]
            public async Task<HttpResponseMessage> GetFileAsync(int FileID) //<-- If your method returns Task have it be named with Async in it
            {
                using (var repo = new MBHDocRepository())
                {
                    var file = await repo.GetSpecificFile(FileID);
                    if (file == null)
                    {
                      throw new HttpResponseException(HttpStatusCode.BadRequest);
                    }

            var stream = File.Open(file.PathLocator, FileMode.Open);
            HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
            response.Content = new StreamContent(stream);
            response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(file.FileType);
            response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment") { FileName=Path.GetFileName(file.PathLocator)};
            return response;
                }
            }

您的客户端代码在这里有两个选项：

static void Main(string[] args)
        {
            using (var http = new WebClient())
            {


    string url = string.Format("{0}api/FileUpload/FileServe?FileID={1}",webApiUrl, fileId);
http.Headers[HttpRequestHeader.ContentType] = "application/octet-stream";
                http.Headers[HttpRequestHeader.Authorization] = "Bearer " + authCookie.Value;
                var response = http.OpenRead(url);
                var fs = new FileStream(String.Format(@"C:\Users\Bailey Miller\Downloads\{0}", GetName(http.ResponseHeaders)), FileMode.Create);
                response.CopyTo(fs); <-- how to move the stream to the actual file, this is not perfect and there are a lot of better examples

            fs.Flush();
            fs.Close();
            }


        }

        private static object GetName(WebHeaderCollection responseHeaders)
        {

            var c_type = responseHeaders.GetValues("Content-Type"); //<-- do a switch on this and return a really weird file name with the correct extension for the mime type.
        var cd = responseHeaders.GetValues("Content-Disposition")[0].Replace("\"", ""); <-- this gets the attachment type and filename param, also removes illegal character " from filename if present
        return cd.Substring(cd.IndexOf("=")+1); <-- extracts the file name
        }