Winforms WebClient.UploadFile() error (System.NotSupportedException)

Posted on 2010-08-13
Medium Priority
Last Modified: 2013-11-26
I am simply trying to upload a file to a URL and the following error message is generated:

System.Net.WebException: An exception occurred during a WebClient request. ---> System.NotSupportedException: The stream does not support concurrent IO read or write operations.
   at System.Net.ConnectStream.InternalWrite(Boolean async, Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
   at System.Net.ConnectStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.WebClient.UploadBitsState.WriteBytes()
   at System.Net.WebClient.UploadBits(WebRequest request, Stream readStream, Byte[] buffer, Byte[] header, Byte[] footer, CompletionDelegate completionDelegate, AsyncOperation asyncOp)
   at System.Net.WebClient.UploadFile(Uri address, String method, String fileName)
   --- End of inner exception stack trace ---
   at System.Net.WebClient.UploadFile(Uri address, String method, String fileName)
   at BREN_iTropics_001.frmUnifiedXML.simpleDataUpload() in frmUnifiedXML.cs:line 61

The offending line is:

byte[] Byte_response = wClient.UploadFile(url, "POST",filename);

can someone see the problem?
private void simpleDataUpload()
        Uri url = new Uri(this.txtFTPServer.Text);
        WebClient wClient = new WebClient();
        NetworkCredential nc = new NetworkCredential("login", "pass");
        wClient.Credentials = nc;
        byte[] Byte_response = wClient.UploadFile(url, "POST", filename);

        wClient.UploadProgressChanged += new UploadProgressChangedEventHandler(wClient_UploadProgressChanged);
        wClient.UploadFileCompleted += new UploadFileCompletedEventHandler(wClient_UploadFileCompleted);

        if (Byte_response != null)
            this.txtMsg.Text += System.Text.Encoding.ASCII.GetString(Byte_response);
    catch (Exception ex)
        this.txtMsg.Text += ex.ToString() + Environment.NewLine;

void wClient_UploadProgressChanged(object sender, UploadProgressChangedEventArgs e)
    this.txtLastResult.Text = "Sent:" + e.BytesSent.ToString() + "  Total:"
                        + e.TotalBytesToSend.ToString() + "   Progress:"
                        + e.ProgressPercentage.ToString() + "%";

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Question by:conrad2010
  • 2

Expert Comment

ID: 33434698
Are you sure you have correct credentials?

Expert Comment

ID: 33434701
And if you have correct credentials, are you sure you have sufficient privileges to perform your upload with them?

Accepted Solution

bkokx earned 2000 total points
ID: 33435351
Problem might be in your "POST" argument.
POST is used for HTTP while for FTP this should be STOR.
These defaults are chosen by the function if you do not specify the argument.

Author Comment

ID: 33438406
yes, the credentials are correct and I have permission to store (tested it in a browser upload version)


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