WPF Programmer's Reference: Windows Presentation Foundation with C# 2010 and .NET 4

Appendix O. Triggers and Animation

This appendix summarizes triggers and animations. For more detailed information, see Chapter 14.

EventTriggers

You can place EventTriggers inside a control's Triggers section to take action when an event occurs. Inside the EventTrigger, you can place actions that should occur when the event takes place.

TEMPTING TRIGGERS

Despite its general-sounding name and the fact that IntelliSense lists other options, the Triggers section can only hold EventTriggers, not property Triggers.

The most useful of these actions include:

• PauseStoryboard — Pauses a Storyboard.

• ResumeStoryboard — Resumes a paused Storyboard.

• SeekStoryboard — Moves the Storyboard to a specific position in its timeline.

• StopStoryboard — Stops a Storyboard. This resets properties to their original values.

• RemoveStoryboard — Stops a Storyboard and frees its resources.

The following code gives a Button an EventTrigger. When the Button raises its Click event, the EventTrigger starts a Storyboard that changes the Button's Canvas.Left property to 300 over a period of 0.5 seconds. The animation's AutoReverse property is True, so after the animation completes, it changes the Canvas.Left property back to its original value.

<Button Name="btnClickMe" Canvas.Left="10" Canvas.Top="10" Content="Click Me">
    <Button.Triggers>

<EventTrigger RoutedEvent="Button.Click"> <EventTrigger.Actions> <BeginStoryboard> <Storyboard> <DoubleAnimation Duration="0:0:0.5" To="300" Storyboard.TargetProperty="(Canvas.Left)" AutoReverse="True"/> ...