WPF MVVM UserControl DataBinding in XAML Not Working

I've got a user control where the DataSource is an ObservableCollection<string>. If I set the DataSource of an instance of my user control via code it works

Chapters.DataSource = vm.ChapterList;

But trying to bind via ht xaml doesn't work

<b:ChapterStack x:Name="Chapters" DataSource="{Binding ChapterList}"></b:ChapterStack>

Other controls on the window开发者_JAVA技巧 are binding to the VM and displaying properly.

What do I have to do to get my usercontrol to bind via xaml?

thanks?

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Make sure you defined the DataSource property of your ChapterStack control as a Dependency Property, because otherwise, you won't be able to bind it.