Playing with WPF/XAML. Creating an AutoCompleteTextBox and using a popup. It's coming along pretty good, but I'm still a noob at this stuff.

I have WinForm that contains an ElementHost which Hosts my testControl.

My testControl is a grid and it contains my AutoCompleteTextBox.

My AutoCompleteTextBox is a TextBox with a Popup which contains a ListBox.

Everything is working good, except I need to close the popup if the user moves the window. The Popup does not stay with the textbox if the window is moved, and closing it is easier than making it follow.

The question is... How do I drill down from my custom control to access an event that will tell me that the form has moved?