Question

I’m creating some custom wp7 silverlight custom controls which register some events on template children in OnApplyTemplate().

I think I must unregister these to prevent a memory leak. But when? I’ll tried the unloaded event – this works but I have a problem with this.
The scenario:
On Page1 I have my custom control. Then navigating away from Page1 to Page2 the Unloaded event of my custom control is called. So far so good. But then I navigate back the events of my custom control aren’t registered again so nothing happens then using that control.

Then should I register and unregister events correctly that everything works as expected and I can’t create a memory leak?

Thanks for your help!

Edit:

Here an example of my OnApplyTemplate() method:

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    _itemsContainer = GetTemplateChild("PART_Items") as ItemsControl;
    if (_itemsContainer != null)
    {
        // When to detach this event for correctly object lifetime?
        _itemsContainer.Tap += ItemsContainer_Tap;
    }
}

Answer 1

I believe what you want is something like this. 🙂

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    this.YourEvent -= new RoutedEventHandler(YourEventHandler);
    this.YourEvent += new RoutedEventHandler(YourEventHandler);
    ...
}

UPDATE

Okay, this is how I do this in my custom control.

        if (this._resizer != null)
        {
            this._resizer.DragStarted -= new DragStartedEventHandler(Resizer_DragStarted);
            this._resizer.DragCompleted -= new DragCompletedEventHandler(Resizer_DragCompleted);
            this._resizer.MouseMove -= new MouseEventHandler(Resizer_MouseMove);
        }

        this._resizer = this.GetTemplateChild("Resizer") as Thumb;

        if (this._resizer != null)
        {
            this._resizer.DragStarted += new DragStartedEventHandler(Resizer_DragStarted);
            this._resizer.DragCompleted += new DragCompletedEventHandler(Resizer_DragCompleted);
            this._resizer.MouseMove += new MouseEventHandler(Resizer_MouseMove);
        }