I’ve discussed how to locate the UIElement associated with an animation’s Completed event a while back for WPF.

Here’s an update for how I do the same thing in Silverlight 2.0. The technique could be used in WPF with a few minor tweaks. I like this method rather than relying on a Storyboard (as I have better control over the completion of individual animations this way). Here’s a page on MSDN that describes various ways to work with animations programmatically in Silverlight.

The Completed event is raised when the animation timeline has ended. The event unfortunately passes only a reference to the sender (which is the Timeline). The EventArgs is empty.

Here’s a chunk of code that sets up an animation programmatically:

BitmapImage bmimg = sender as BitmapImage;

Game.Dispatcher.BeginInvoke(delegate()
{
    DoubleAnimation animation = new DoubleAnimation();
    animation.To = 0.0;
    animation.From = 1.0;
    animation.Duration = new Duration(TimeSpan.FromSeconds(2 + Game.Randomizer.Next(5)));
    animation.SetValue(Page.ImageProperty, bmimg);
    animation.Completed += new EventHandler(animation_Completed);

    Image img = bmimg.GetValue(Page.ImageProperty) as Image;
    Storyboard sb = new Storyboard();
    sb.Children.Add(animation);
    Storyboard.SetTarget(animation, img);
    Storyboard.SetTargetProperty(animation, new PropertyPath("Opacity"));
    sb.Begin();
});
}

The significant line above is the animation SetValue. Here, I’m using the power of the Dependency Object. I can attach new properties to the animation directly!

public static readonly DependencyProperty ImageProperty =
    DependencyProperty.RegisterAttached("Image", typeof(DependencyObject), typeof(Page), null);

I’ve created a new DependencyProperty (as an attached property) called ImageProperty. There’s not much meaning to the name — other than it makes sense in the context in which I’m using it in the larger application.

void animation_Completed(object sender, EventArgs e)
{
    Timeline t = sender as Timeline;
    if (t != null)
    {
        BitmapImage img = t.GetValue(Page.ImageProperty) as BitmapImage;
        if (img != null)
        {
            // do something here...
        }
    }
}  

In the completed event, I retrieve the attached property’s value from the animation (which I’ve cast to one of the base types, a Timeline). Then, you could do whatever you want….

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