A plea to Microsoft
Keine Überlast für OnVisibilityChanged stimmt mit dem Delegat System.Windows.DependencyPropertyChangedEventHandler überein. ...
Microsoft, please stop translating exception messages for a programming language that is otherwise completely English, especially if you let it be done by a machine. The above is an error from the compiler! Never ever meant to be seen by an end user, but a person proficient in programming with the .NET framework. This is annoying, it hinders searching for solutions on the Internet, in short, it is crap! Please, stop it!
Überlast here refers to method overloading, i.e. the method I was passing to a delegate was wrong in signature.