How can I use a DoubleAnimation to rotate the textblock ?

The following example uses a DoubleAnimation to rotate the textblock. The textblock performs a full rotation over a duration of 20 seconds and then continues to repeat the rotation.

[XAML]

<TextBlock
  Name='MyRotatingText'
  Margin='20' 
  Width='640' Height='100' FontSize='48' FontWeight='Bold' Foreground='Teal' 
  >
  This is rotating text
  <TextBlock.RenderTransform>
    <RotateTransform x:Name='MyRotateTransform' Angle='0' CenterX='230' CenterY='25'/>
  </TextBlock.RenderTransform>

  <!-- Animates the text block’s rotation. -->
  <TextBlock.Triggers>
    <EventTrigger RoutedEvent='TextBlock.Loaded'>
      <BeginStoryboard>
        <Storyboard>
          <DoubleAnimation
            Storyboard.TargetName='MyRotateTransform' 
            Storyboard.TargetProperty='(RotateTransform.Angle)'
            From='0.0' To='360' Duration='0:0:10' 
            RepeatBehavior='Forever' />
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </TextBlock.Triggers>
</TextBlock>