使用HttpWebRequest上传文件—无法上传

下面是代码-上传文件到uri。我不能上传。有什么问题吗?

string fileToUpload = @"F:''upload_file.txt";
FileStream rdr = new FileStream(fileToUpload, FileMode.Open);
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://localhost:8080/upload.txt"); //Given URI is exists
req.Method = "POST"; 
req.ContentLength = rdr.Length;
req.AllowWriteStreamBuffering = true;
Stream reqStream = req.GetRequestStream();
Console.WriteLine(rdr.Length);                
byte[] inData = new byte[rdr.Length];
// Get data from upload file to inData 
int bytesRead = rdr.Read(inData, 0, (int)rdr.Length);
// put data into request stream
reqStream.Write(inData, 0, (int)rdr.Length);
rdr.Close();
req.GetResponse();
// after uploading close stream 
reqStream.Close();