Call MessageBox from async thread with Form1 as parent

Question

After clicking button1 placed on form1, program is checking if the new version is available (via internet), but doing this in the new thread (not to freeze the form during check).
When the new version is found or not, the appropriate MessageBox is shown, but it has no parent (because it was called from the thread, not directly from the form1).

How to make the MessageBox display with form1 as a parent?

Answer 1

this.Invoke(new Action(() => { MessageBox.Show(this, "text"); }));

This will switch to main thread and show MessageBox with form1 parent.

Answer 2

While the selected answer provides a nice way of displaying the MessageBox from an asynchronous thread, it doesn't handle the case where you want to retrieve the DialogResult from that particular MessageBox being shown.

If you are looking to return a DialogResult from the invoked MessageBox displayed on top of the Form. Then you need to use the Func delegate instead of the Action delegate.

Action delegates always return void while Func has a return value.

Here is a little method that I devised to handle this particular scenario:

private DialogResult BackgroundThreadMessageBox(IWin32Window owner, string text)
{
   if (this.InvokeRequired)
   {
      return (DialogResult) this.Invoke(new Func<DialogResult>(
                             () => { return MessageBox.Show(owner, text); }));
   }
   else
   {
      return MessageBox.Show(owner, text);
   }
}

Although this isn't typically considered best practice or design it will work in a pinch.

Answer 3

  if ( Form1.InvokeRequired ) {
            Form1.Invoke((Action)delegate{MessageBox.Show(Form1,"Hello");});
        }