What really got me confused for 2 days, is the way that you need to import the System.Windows.Controls assembly before all controls from the System.Windows.Controls namespace become available!
You need to add the System.Windows.Controls.dll to AppManifest.xml... and then the following magic line(s):

clr.AddReference("System.Windows.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")
clr.AddReference(" System.Windows.Controls.Extended, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")

Please add it in a prominent place to your docs, otherwise you'll get confused when trying to run this line:

from System.Windows.Controls import ListBoxItem
Koen | Homepage | 08/03/11 - 7:58 pm | #

Yeah - that confused me too. Especially that adding the reference would fail completely until you use the full strong name.

I'm covering this in my talks.
Michael Foord | Homepage | 08/03/11 - 8:14 pm | #