I'm guessing that you've declared the dtVenues
collection for your ComboBox
es in the code behind of your Window
and set the Window.DataContext
property value to the code behind class in one way or another. If that is true, then I believe that you need to change your Binding
slightly to address the Window.DataContext
:
<ComboBox ItemsSource="{Binding Path=DataContext.dtVenues, ElementName=MyWindow}"... />