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How can I bind 2 comboboxes in 2 different WPF windows to the same observable collection?

Posted By:      Posted Date: August 29, 2010    Points: 0   Category :WPF
I have a pretty simple (or deceptively not so) question. I have a WPF application that has a nicely bound combo to an ObservableCollection. I am trying to correctly implement MVVM. One thing I am trying to do (as a test for other things I need) is to have a combo in a popup window have the same content (2-way data bound) as the combo on the main window. I have the main window set up with no issues. <     ComboBox Height="23" HorizontalAlignment="Left" Margin="110,197,0,0" Name="comboBox1" VerticalAlignment="Top" Width="194" ItemsSource="{Binding MyStuff}"/> where "MyStuff" is an ObservableCollection. My problem comes when I create a new wpf application (separate project), put a combo on it, launch it from a button in the first project, and try to bind the combo to the same ItemsSource. I can't seem to figure out the syntax. My 2 issues are as follows: 1. I think the XMAL in the child window needs to have something like this: <     ComboBox Height="23" HorizontalAlignment="Left" Margin="110,257,0,0" Name="comboBox1" VerticalAlignment="Top" Width="194" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ObservableCollection}, AncestorLevel=2}

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