Asynchronous webrequest problem

[wajih boukaram]

Hi I began writing a c# program and everything was going ok until i tried to use asynchronous webrequests instead of synchronous ones (since the UI would be unresponsive while it was fetching the response) and i have a slight problem: the user signs in by clicking a button on the form - the program fetches the data from the server asynchronously - the problem is with the callback function - when debugging i see that the request was successfully completed but when i try to access any controls (like filling a textbox with the response) from the callback function it just stop executing the function - no exceptions, no errors - i can still interact with the program but it just wont alter anything to do with the form's controls (the form's data members however were being altered with no issues - a string and an integer to be exact) I'm a newbie at c# and i just started using the asynchronous method so if im doing sumthing wrong please advise thank you for your time

[Christian Graus]

A good first step would be to post some code, so we can offer some advice on it.

Christian Graus - C++ MVP

[wajih boukaram]

Hi thanks for your quick reply these are methods of my MainForm class (base class is Form) private void getResult(String url, AsyncCallback callback) { try { HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url); request.Method = "GET"; if(useCompression) request.Headers.Add("Accept-Encoding: gzip,deflate"); request.CookieContainer = mainCookie; request.AllowAutoRedirect = true; request.AllowWriteStreamBuffering = true; IAsyncResult result = request.BeginGetResponse(callback, request); } catch (WebException wex) { MessageBox.Show("Error Connecting: Check your connection settings...\nDetails: " + wex.Status.ToString()); return; } } private void SignInButton_Click(object sender, EventArgs e) { DisableSignInControls(); String url = mirror + "signin.aspx?user=" + UserNameComboBox.Text + "&pass=" + PasswordTextBox.Text; mainCookie = new CookieContainer(); getResult(url, new AsyncCallback(signIn)); } private void signIn(IAsyncResult result) { HttpWebRequest request = (HttpWebRequest)result.AsyncState; HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(result); String responseResult = (useCompression ? decompressResponse(response) : new StreamReader(response.GetResponseStream()).ReadToEnd()); int i = responseResult.IndexOf("<response>"); if (i < 0) MessageBox.Show("Corrupt response. Please try again."); else { int j = responseResult.IndexOf("</response>"); String temp = responseResult.Substring(i + 10, j - i - 10); if (temp != "") { String[] returnValues = temp.Split('|'); if (returnValues.Length == 1) MessageBox.Show(returnValues[0]); else { sid = returnValues[0]; num_messages = int.Parse(returnValues[1]); MessageNumber.Text = "Messages: Left " + num_messages; SignInGroupBox.Visible = fal

[Christian Graus]

wajih.boukaram wrote:

IAsyncResult result = request.BeginGetResponse(callback, request);

Doesn't result just get discarded ? And where is the callback hooked up to a method ?

Christian Graus - C++ MVP

[wajih boukaram]

yea it does but all that matters is the callback function (which i assigned when i called getResult(url, new AsyncCallback(signIn)); so its hooked up to signIn it works fine the way it is - only problem is changing the form's control values - i think it might have something to do with threading because if i try calling the function a second time (I hate c# sometimes) it says sumthin about accessing an object that was not created on the same thread - when i first tried to do this asynchronously i actually just created a new thread that called my initial signIn function which was just a regular function and not a callback - i got the same error message when acessing the controls. any suggestions? thanks for your replies.