c#HttpWebRequest.GetResponse()返回错误:(404)找不到

我有一个Asp.net控制台应用程序，我使用以下代码上传文件：

byte[] buffer = memoryStream.ToArray();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.ContentType = "application/octet-stream";
request.Method = "POST";
request.ContentLength = buffer.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(buffer, 0, buffer.Length);
dataStream.Close();
response = (HttpWebResponse)request.GetResponse();

如果缓冲区大小为8MB，则HttpWebResponse工作正常，但如果缓冲区尺寸为32MB，则请求正常。GetResponse（）返回错误：

远程服务器返回错误：（404）找不到。