What can I do to find out which part of my code throws this exception or where it happens. Is there a way to show/visualize this in VS? Debugger options?
In Visual Studio, choose Debug then Exceptions.
In the Exceptions window, tick Thrown on the Common Language Runtime Exceptions row.
Now whenever an exception is thrown, the debugger will break on the offending line. You can also expand the selection to only include the exceptions of interest.
Visual Studio 2017
You can find this under Debug.Windows.Exception Settings