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My main form is performing long operations.In order to tell the user that the application is processing and not freezing I wanted to implement a progress bar in another form.

It seems that you can't interact with controls if you're not on the main thread. I tried to implement backgroundworker as suggested in the link below but without success.

http://perschluter.com/show-progress-dialog-during-long-process-c-sharp/

Same thing with Task-based Asynchronous Pattern

How to update the GUI from another thread in C#?

The closer to success I've been is with encapsulating the call of the progress bar form in another thread :

Form_Process f_p = new Form_Process();
Thread newWindowThread = new Thread(new ThreadStart(() =>
{
    // Create and show the Window

    f_p.ShowDialog();
    // Start the Dispatcher Processing
    System.Windows.Threading.Dispatcher.Run();
}));

// Set the apartment state
newWindowThread.SetApartmentState(ApartmentState.STA);
// Make the thread a background thread
newWindowThread.IsBackground = true;
// Start the thread
newWindowThread.Start();

f_p.label_Progression.Text = "Call to exe";
f_p.progressBar1.Value = 30;
f_p.Refresh();

But when I call a function in the main thread and I try to update the progress bar, the cross-thread exception is logically lifted.

Am I missing something ?

Community
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bill
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1 Answers1

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You can't set control properties on a form from a different thread. You need an invokation to do this.

On your form, create a function:

public void SetProgressText(string value) {
     if (this.InvokeRequired) {
         Action<string> progressDelegate = this.SetProgressText;
         progressDelegate.Invoke(value);
     } else {
         label_Progression.Text = value;
     }
}

And then, instead of 

f_p.label_Progression.Text = "Call to exe";

call

f_p.SetProgressText("Call to exe");

Same for the progress bar. You can put all invokations inside one function though.

LInsoDeTeh
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  • Thanks a lot your solution seems good ! I bypassed the problem by setting global variable and updating the form through a timer. – bill Jul 22 '15 at 10:06
  • Be careful with that timer solution. It's dirty. It'll probably not be a problem with just a variable, but as soon as you have bigger objects or collections which are accessed by multiple threads at the same time, you'll get into trouble. – LInsoDeTeh Jul 22 '15 at 10:43