Question

I want to be able to set a property with an EventTrigger, there’s a number of problems with this.

1) EventTriggers only support Actions, so I must use a storyBoard to set my properties.

2) Once I use a storyboard, I have two options:

• Stop: Once the animation has stopped the value reverts back to before the animation started
• HoldEnd: This locks the property, so that neither code, nor user interaction can change the property that the animation is holding.

In the below example, I want to set the IsChecked property to False when the button is clicked and I want the user to be able to change the IsChecked and/or I want to be able to change the property in code.

Example:

<EventTrigger
    SourceName="myButton"
    RoutedEvent="Button.Click">
    <EventTrigger.Actions>
        <BeginStoryboard>
            <Storyboard>
                <BooleanAnimationUsingKeyFrames
                    Storyboard.TargetName="myCheckBox"
                    Storyboard.TargetProperty="IsChecked"
                    FillBehavior="Stop">
                    <DiscreteBooleanKeyFrame
                        KeyTime="00:00:00"
                        Value="False" />
                </BooleanAnimationUsingKeyFrames>
            </Storyboard>
        </BeginStoryboard>
    </EventTrigger.Actions>
</EventTrigger>

I realize that I can use the “Completed” event after the storyboard completes to set the value to False. However, in this instance I want to contain the logic within the XAML, as this logic will be used on a custom control and is only specific to the UI.

Answer 1

As much as I love XAML, for this kinds of tasks I switch to code behind. Attached behaviors are a good pattern for this. Keep in mind, Expression Blend 3 provides a standard way to program and use behaviors. There are a few existing ones on the Expression Community Site.