You can use the EventTrigger trigger in a Windows Phone project to invoke an action based on an event such as a mouse click, a page loading, or another interaction. EventTrigger is the default trigger for actions that you define in Microsoft Expression Blend.
To add an EventTrigger to a Windows Phone project
In the Assets panel, click Behaviors, and then drag the behavior that you want onto the object that you want to apply the behavior to. The Trigger category appears in the Properties panel.
In the Trigger category, in the EventName drop-down list, select the event that you want to trigger the action.
Click Show advanced properties. In the SourceName box, select the element that will enable the event. By default, the SourceName is the element that contains an action. You can use the Artboard Element Picker to select the element directly on the artboard.
To see a sample of this behavior, visit the Expression Community Gallery .