Why Would a Dependency-Property Implementation Crash My Application When I Provide a Default Value?

Question

Why would a dependency-property implementation crash my application when I provide a default value?

This segment of code is in the class declaration for my UserCon

Answer 1

Short answer:

Dependency property default values need to be thread safe (e.g. inherit from System.Windows.Freezable) but System.Windows.Forms.Rectangle isn't.

Long answer:

http://social.msdn.microsoft.com/forums/en-US/wpf/thread/2cb12481-ef86-40b7-8333-443598d89933/

Hint:

If you are using Visual Studio it really helps to let the IDE break on every exception being thrown. Just go to "Debug" -> "Exceptions" and check "Common Language Runtime Exceptions" "Thrown".

Then you'll be prompted and get the exception message which in your case looks like this: "Additional information: Default value for the 'Rect' property cannot be bound to a specific thread."