Threading trouble with windows forms

Question

Alright so I am having a hard time figuring out how to wait for the thread to finish before continuing along with the code without freezing up the windows form..

example code:

var ct = new System.Threading.Thread(solve);
ct.IsBackground = true;
ct.Name = "Solving";
//start our thread
ct.Start();
ct.Join();
label33.Invoke((MethodInvoker)delegate { label33.Text = "Submitting..."; });
clickPost("name", textBox27.Text);

score 1 · Answer 1 · answered Feb 29 '12 at 07:04

The call to ct.Join() only has one purpose - to block until the thread in question completes.

If you don't want to block, you need to handle notification of the completion of the background "work" via some other mechanism, such as an event.

This is greatly simplified for Windows Forms by using a BackgroundWorker, which does the notification for you (on the correct user interface thread).

score 0 · Answer 2 · answered Feb 29 '12 at 07:15

0

If I understand you correctly all you need is to create callback for some async operation. You can use delegate's BeginInvoke callback parameter. Keep in mind the delegate and its callback will be executed in own thread:

Action backgroundAction = new Action(DoAction);
backgroundAction.BeginInvoke(ActionCallback, null);

private void DoAction()
{
    //some background task
}

private void ActionCallback(IAsyncResult result)
{
   //will be executed after
}

answered Feb 29 '12 at 07:15

Igor Khramtsov

39
2

Shouldn't you be calling `EndInvoke` somewhere? – John Saunders Feb 29 '12 at 07:20
EndInvoke can be used if you need to get some result from DoAction(). In my example DoAction() declared as void. If you use another delegate with return value you right the only way to get this result is using EndInvoke. – Igor Khramtsov Feb 29 '12 at 08:00
I'm having a problem with Action... "Using the generic type 'System.Action' requires 1 type arguments" – user372671 Feb 29 '12 at 08:03
Yes, I forgot about exceptions... Thank you. – Igor Khramtsov Feb 29 '12 at 08:05
I wonder where you get this error? If you use my code there are no such error. I dont use generic version of Action. – Igor Khramtsov Feb 29 '12 at 08:13
I am using your code exactly and its giving me the generic type error i said when i try to compile. – user372671 Feb 29 '12 at 08:24
What version of .NET Framework you use? Action class appeared in 3.5. So my example works on 3.5 Framework or higher. – Igor Khramtsov Feb 29 '12 at 08:31
ah yes, that was the issue. I am now using a higher framework and is not throwing any errors. Thank you. – user372671 Feb 29 '12 at 08:35
Is it possible to do the same except have the ActionCallback code to happen within the ui and not within the thread? – user372671 Feb 29 '12 at 09:19
There are many threads on SO where this problem was discussed. For example [link](http://stackoverflow.com/questions/4599902/c-how-to-force-calling-a-method-from-the-main-thread-by-signaling-in-some-wa) – Igor Khramtsov Feb 29 '12 at 09:40

Threading trouble with windows forms

2 Answers2