caeruleum | Daily Bruin 's WordPress theme and special projects | Content Management System library

The data source handling should be moved to a control which is the common parent of the ComboBox and the Frame, in this case I chose the MainWindow.

You should add the required DependecyProperty definitions to the MainWindow which can be used for data binding for the ComboBox.ItemsSource, ComboBox.SelectedItem and the Frame.DataContext.

For the XML handling I replaced the XMLDataProvider with an XElement data source which allows LINQ To XML in order to comfortably filter or traverse the XML object tree in C#.

Now the ComboBox binds to a collection of XElement items representing XML color nodes. The selected ComboBox item is a single XML color element. The descendant plant nodes of color are used to set the Frame.DataContext, which is inherited to the Page.DataContext. The ListBox in the Page now binds its ItemsSource directly to the DataContext which is the MainWindow.PlantsOfSelectedColor property. Alternatively, e.g. if you need to set the Page.DataContext to something different, you can let the Binding traverse the visual tree to find the MainWindow.PlantsOfSelectedColor using RelativeSource FindAncestor for the Binding.RelativeSource of ListBox.ItemsSource.

MainWindow.xaml.cs