Hello, I have a Silverlight application in which I implemented MVVM pattern. In my application there is a child window on which I have ComboBox. I bound ItemsSource and SelectedItem of my combobox to a property (typeof ObservableCollection) and property of MyType appropriately. MyType is a "MODEL" derived from INotifyPropertyChanged. When my window is loaded I set values to this properties. But my combobox doesn't display selected item. I found that when I set property which is bound to selected item (in ViewModel), the PropertyChanged event is null. Can anyone help me. Thanks.