WPF and MessageBox in Dispatcher.Invoke

Painful, painful, painful.

That was my experience when a WPF application I was creating would display a MessageBox on startup.  For efficiency many things were going on simultaneously, and most was tripped off with Dispatcher.BeginInvoke.  If something needed user interaction at startup, a MessageBox would display to get the user's attention.  The problem was, it was not modal, so the user would see the MessageBox flash and disappear, with the default value selected (which was very problematic).

A google search finally revealed the answer.  When using Dispatcher.Invoke, you need to pass the owning window to MessageBox:

MessageBox.Show(this, "message");