RE: WPF MessageBox...

This entire thread is dealing with the MessageBox class which is part of WPF.

If you are using Windows Forms then there is a different MessageBox class which is within the System.Windows.Forms namespace that is close to but not identical to the one shown above for WPF.

Please see the MSDN entry here:

In Windows Forms the equivalent would be something like the following:
(namespace System.Windows.Forms should be included in the namespace list by default)

       evaluate type MessageBox::Show(
            "Mein Text",
            "Kopfzeile",
             type MessageBoxButtons::YesNo
             type MessageBoxIcon::Question
             type MessageBoxDefaultButton::Button1
             type MessageBoxOptions::RightAlign)
         when type DialogResult::Yes
              continue
           when type DialogResult::No
              continue
        end-evaluate.