Debug.Writeline and foreach- Error??

Hello,
I wrote a COM Addin using C#. Now I saw twice:
1. everytime I interate a Collection (i.e. Bookmarks) with foreach, this
works but after having finished the function. The COM Addin hangs or do not
trap the events to call its functions.
2. everytime I make an output with Debug.WriteLine, this works but after
having finished the function. The COM Addin hangs or do not trap the events
to call its functions.

Does anybvody know where this comes from?
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Best Regards

Patrick Jox