HTTP上传进度

Question

我正在将一些表单数据（包括文件）上传到网络服务器，并且需要跟踪上传进度。我通过将我的上传数据一点一点地复制到HttpWebRequest的请求流中，并根据复制的字节数和总字节数更新进度条。根据另一个网站的说法，这将缓冲所有内容，之后实际的网络传输需要更长的时间。我应该设置 request.AllowWriteStreamBuffering = false; 来防止缓冲。不幸的是，当我这样做时，request.GetResponse() 方法会永远阻塞。

下面是一些示例代码：

HttpWebRequest request = (HttpWebRequest) HttpWebRequest.Create(uri);
request.AllowAutoRedirect = false;
request.Method = "POST";
request.ContentType = "multipart/form-data; boundary=" + multipartBoundary;
Stream reqStream = request.GetRequestStream();
request.AllowWriteStreamBuffering = false;
postStream.Seek(0, SeekOrigin.Begin);
byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = postStream.Read(buffer, 0, buffer.Length)) > 0)
{
    reqStream.Write(buffer, 0, bytesRead);
    int percentage = (int) (postStream.Position * 100 / postStream.Length);
    backgroundWorker.ReportProgress(percentage);
}
reqStream.Close();
HttpWebResponse response = (HttpWebResponse) request.GetResponse();

当我不设置 AllowWriteStreamBuffering 时一切正常。这里有什么问题？

Answer 1

问题是设置 AllowWriteStreamBuffering 太晚了。这很好用：

HttpWebRequest request = (HttpWebRequest) HttpWebRequest.Create(uri);
request.AllowWriteStreamBuffering = false;
request.SendChunked = true;
request.AllowAutoRedirect = false;
request.Method = "POST";
...

通过预先设置AllowWriteStreamBuffering，它还异常告诉我必须设置SendChunked或指定内容长度（我现在手头没有）。

HTTP上传进度

HTTP upload progress

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