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Messagebox.showdialog() and multithread

Posted on 2006-11-06
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Last Modified: 2012-08-13
Hello. In my c# app I want to use a Form as a dialog showing progress of time consuming operation. I mean:
I have the mainform, running on the unique main thread. When user click button a long update of data to a remote webservice is launched. I want the following beahvior: user click button, data update runs on the main thread (cause it update main form objects too); while the webservice is running I want that a form dialog is shown to the user (running on a second thread). The form will contain a progressbar update with the progress of the application. When the webservice finished, the second form will close. Here is my code:

//..main Thread:
System.Threading.Thread TR1 = new System.Threading.Thread(u);
Italia(); // <-- Webservice taking long time
TR1.Start();

private void u()
        {
            int y = this.Location.Y;
            int nav = ((SisCos)MdiParent).NavTree.Width;
            int parentlocx = this.MdiParent.Location.X;
            int parentlocy = this.MdiParent.Location.Y;
            Point pnt = new Point(parentlocx + nav + 5, parentlocy + y + 10);

            SisCosExplorer.UIsVarie.MessBoxSisCos MB = new SisCosExplorer.UIsVarie.MessBoxSisCos(); // <-- Derived from Form class: it's a form without border
            MB.Height = Convert.ToInt16(System.Math.Round(this.Height * .95, 0));
            MB.Width = Convert.ToInt16(System.Math.Round(this.Width * .95, 0));
            MB.Location = pnt;

            MB.ShowDialog();
        }

It' s all working great except for one thing: The second form (MB) it's not working like a dialog (even if i call MB.Showdialog). I mean, if the user click on the main form, main form is focused. And I don't want it at all cause the webservice it's uplaoding the main form. I think it's a thread problem. What can I do to make MB working like a real Dialog?
Thanks in advance
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Question by:puckkk
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AlexFM earned 500 total points
Comment Utility
This happens because you show modal dialog in the worker thread. Dialog is modal only inside of thread which created it.
General approach is creating all UI elements in the main thread, and running worker thread in background. Worker thread doesn't have any UI elements. It can pass progress and any other information to UI using Invoke or BeginInvoke methods:
http://www.codeproject.com/csharp/workerthread.asp

If you want to continue with your current approach, try to disable main form for the time when MB dialog is active. This can prevent main form to be activated by mouse (I didn't test this because I always use first way to run threads).
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by:puckkk
Comment Utility
I used the first (and best) way reading the article. That's exactyl what i neede. Thx a lot.
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