Show Form Always On Top Of Other Form Which is Created In Different Thread

Question

Possible Duplicate:
Cross-thread exception when setting WinForms.Form owner - how to do it right?

I'm newbie to C# Windows Forms Application Development.

In my application main form we create new forms in other thread like below.

Task.Factory.StartNew(
            () =>
            {
                PlotForm plotForm = new PlotForm();
                Application.Run(plotForm);
            });

I want to display that forms always on top of the main form. There is a topmost property in Forms. If i set it to true they are also on top of the other forms.

In the internet it is said that solution is to set owner property and when i set this property , i got cross thread operation because forms are created different threads.

Task.Factory.StartNew(
            () =>
            {
                PlotForm plotForm = new PlotForm();
                plotForm.Owner = this;
                Application.Run(plotForm);
            });

Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on.

Do you know a solution?

Thanks.

This is the only case I know where the cross-threading check is not accurate. Windows does in fact support this. Running a form on a thread-pool thread however is *not* supported, the thread must be an STA apartment. A plain Thread object and a call to its SetApartmentState method is required. Don't do this. — Hans Passant, Oct 14 '12 at 11:30

score 1 · Answer 1 · answered Oct 14 '12 at 09:06

For cross thread operations you need to use Invoke. The "invoke" call tells the form "Please execute this code in your thread rather than mine."

Task.Factory.StartNew(
            () =>
            {
                PlotForm plotForm = new PlotForm ();
                this.Invoke((MethodInvoker)delegate()
                {                   
                   plotForm.Owner = a;
                   plotForm.Show();
                });
            });

Show Form Always On Top Of Other Form Which is Created In Different Thread

1 Answers1