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How to: Animate the Thickness of a Border by Using Key Frames

This example shows how to animate the BorderThickness property of a Border.

The following example uses the ThicknessAnimationUsingKeyFrames class to animate the BorderThickness property of a Border. This animation uses three key frames in the following manner:

  1. During the first half second, uses an instance of the LinearThicknessKeyFrame class to gradually increase the thickness of the border. The example uses LinearThicknessKeyFrame to create a smooth linear increase between values.

  2. At the end of the next half second, uses an instance of the DiscreteThicknessKeyFrame class to suddenly increase the thickness of the border. Discrete key frames like those derived from DiscreteThicknessKeyFrame create sudden jumps between values, that is, the movement of the animation is jerky.

  3. During the final two seconds, uses an instance of the SplineThicknessKeyFrame class to decrease the thickness of the border. Spline key frames like those derived from SplineThicknessKeyFrame create a variable transition between values according to the values of the KeySpline property. In this key frame, the animation starts off slow and speeds up exponentially toward the end of the time segment.

<!-- This example shows how to use the ThicknessAnimationUsingKeyFrames to create
an animation on the BorderThickness property of a Border. -->
<Page  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  x:Class="Microsoft.Samples.KeyFrameExamples.ThicknessAnimationUsingKeyFramesExample"
  Name="myRootElement"
  WindowTitle="ThicknessAnimationUsingKeyFrames Example">

  <StackPanel Orientation="Vertical" HorizontalAlignment="Center">
    <Border Background="#99FFFFFF" BorderBrush="#CCCCFF" BorderThickness="1"
    Margin="0,60,0,20" Padding="20"  >
      <Border.Triggers>
        <EventTrigger RoutedEvent="Border.Loaded">
          <BeginStoryboard>
            <Storyboard>

              <!-- Animating the BorderThickness property uses 3 KeyFrames. -->
              <ThicknessAnimationUsingKeyFrames
                Storyboard.TargetProperty="BorderThickness"
                Duration="0:0:5" FillBehavior="HoldEnd" RepeatBehavior="Forever">
                <ThicknessAnimationUsingKeyFrames.KeyFrames>

                  <!-- Using a LinearThicknessKeyFrame, thickness increases gradually
                  over the first half second of the animation. -->
                  <LinearThicknessKeyFrame KeyTime="0:0:0.5">
                    <LinearThicknessKeyFrame.Value>
                      <Thickness Left="8" Right="8" Top="6" Bottom="6" />
                    </LinearThicknessKeyFrame.Value>
                  </LinearThicknessKeyFrame>

                  <!-- Using a DiscreteThicknessKeyFrame, thickness increases suddenly
                  after the first second of the animation. -->
                  <DiscreteThicknessKeyFrame KeyTime="0:0:1">
                    <DiscreteThicknessKeyFrame.Value>
                      <Thickness Left="28" Right="28" Top="24" Bottom="24" />
                    </DiscreteThicknessKeyFrame.Value>
                  </DiscreteThicknessKeyFrame>

                  <!-- Using a SplineThicknessKeyFrame, thickness decreases slowly at first
                  and then suddenly contracts. This KeyFrame takes 2 seconds. -->
                  <SplineThicknessKeyFrame KeySpline="0.6,0.0 0.9,0.00" KeyTime="0:0:3">
                    <SplineThicknessKeyFrame.Value>
                      <Thickness Left="1" Right="1" Top="1" Bottom="8" />
                    </SplineThicknessKeyFrame.Value>
                  </SplineThicknessKeyFrame>

                </ThicknessAnimationUsingKeyFrames.KeyFrames>
              </ThicknessAnimationUsingKeyFrames>
            </Storyboard>
          </BeginStoryboard>
        </EventTrigger>
      </Border.Triggers>

      <TextBlock>
        This example shows how to use the ThicknessAnimationUsingKeyFrames to create
        an animation on the BorderThickness property of a Border. 
      </TextBlock>
    </Border>

  </StackPanel>
</Page>

For the complete sample, see KeyFrame Animation Sample.

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