Timeline.Completed Event

public event EventHandler Completed

<timeline Completed="eventhandler"/>

<Canvas
  Width="200" Height="200"
  Background="White"
  x:Name="Page">
  <Canvas.Triggers>
    <EventTrigger RoutedEvent="Canvas.Loaded">
      <BeginStoryboard>
        <Storyboard x:Name="ColorStoryboard" Completed="onCompleted">

          <!-- Animate the background color of the canvas from red to green
               over 4 seconds. -->
          <ColorAnimation BeginTime="00:00:00" Storyboard.TargetName="Page" 
           Storyboard.TargetProperty="(Panel.Background).(SolidColorBrush.Color)"
           From="Red" To="Green" Duration="0:0:4" />

        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </Canvas.Triggers>
</Canvas>

function onCompleted(sender, eventArgs)
{

  alert("Storyboard has completed!");

}