Question

I’ve got a ListView which is bound to a list of objects. When I select an item in the ListView, I catch a SelectionChanged event and then pass the selected object off to a details view.

protected void list_selectionChanged(object sender, SelectionChangedEventArgs e) {
    var myObject = theList.SelectedItem as MyObjectType;

    detailsView.DataContext = myObject;
}

detailsView is a UserControl in the same WPF as the ListView. It contains some XAML like so:

<Label Content="{Binding Path=deviceId}"></Label>
<l:MyUc deviceId="{Binding Path=deviceId}" />

Inside MyUC, I’ve got a DependencyProperty defined:

public static readonly DependencyProperty deviceIdProperty = DependencyProperty.Register("deviceId", typeof(Guid), typeof(MyUC), new FrameworkPropertyMetadata(null));

public Guid deviceId {
    get { return (Guid)GetValue(deviceIdProperty); }
    set { SetValue(deviceIdProperty, value); }
}

The Label shows the deviceId, but the property inside MyUC never gets set.

Can anyone spot my mistake?

Answer 1

When you use a Dependency Property in XAML, the set method never gets called. If you want to “see” this set, you need to add a property changed callback, as the binding mechanism directly sets the dependency property without your setter.

For details on how to implement this, see the PropertyChanged callbacks section of MSDN.