wpf attached property: where to unsubscribe from event handling?

Question

I have a dependency property (bool) which enables a behavior in a textbox. The property changed callback subscribes to some eventhandlers:

static void MyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is TextBox && e.NewValue != null)
        {
            var tb = d as TextBox;

            if ((bool)e.NewValue)
            {
                tb.Loaded += TextBox_OnLoaded;
                tb.MouseLeftButtonDown += TextBox_OnMouseLeftButtonDown;
            }
            else
            {
                tb.Loaded -= TextBox_OnLoaded;
                tb.MouseLeftButtonDown -= TextBox_OnMouseLeftButtonDown;
            }
        }
    }

in my Xaml, i have:

<TextBox
        customdp:MyTextBoxBehavior.EnableBehavior="True">
</TextBox>

Leaving this, the behavior works fine. But the unsubscribing never is executed! So Where do I have to put:

customdp:MyTextBoxBehavior.EnableBehavior="False"

???

Here is another case: 2) I have a listview and subscribed inside OnLoaded() to events of sub items in the visual tree. Reason: I don't want to add attached properties to each listviewitem.

static void ListView_OnLoaded(object sender, RoutedEventArgs routedEventArgs)
    {
        var lv = sender as ListView;
        if (lv != null)
        {
            foreach (TextBox tb in lv.Items)
            {
                 tb.LostFocus += TextBox_OnLostFocus;
            }
        }
    }

Idea: unsibscribe in:

ListView_OnUnLoaded(..)
{
   // Items already empty 
}

...where to unsubscribe ?

Answer 1

At the moment where you are able to do tb.Loaded += you also have access to tb.Unloaded. Use that opportunity to add your cleanup code which will unsubscribe the Loaded event -- and also the Unloaded event.