An animation updates the value of a property over a period of time. An animation effect can be subtle, such as moving a Shape a few pixels left and right, or dramatic, such as enlarging an object to 200 times its original size while spinning it and changing its color. To create an animation in Windows Presentation Foundation (WPF), you associate an animation with an object's property value.

Target Values

The DoubleAnimation class creates a transition between two target values. To set its target values, use its From, To, and By properties. The following table summarizes how the From, To, and By properties may be used together or separately to determine an animation's target values.

Properties specified	Resulting behavior
From	The animation progresses from the value specified by the From property to the base value of the property being animated or to a previous animation's output value, depending on how the previous animation is configured.
From and To	The animation progresses from the value specified by the From property to the value specified by the To property.
From and By	The animation progresses from the value specified by the From property to the value specified by the sum of the From and By properties.
To	The animation progresses from the animated property's base value or a previous animation's output value to the value specified by the To property.
By	The animation progresses from the base value of the property being animated or a previous animation's output value to the sum of that value and the value specified by the By property.

Note:
If you set both the To and By properties, the To property takes precedence and the By property is ignored.

To use other interpolation methods or animate between more than two target values, use a DoubleAnimationUsingKeyFrames object.

Freezable Features

To make a framework element fade in and out of view, you can animate its Opacity property or you can animate the Opacity property of the Brush (or brushes) used to paint it. Animating the element's opacity makes it and its children fade in and out of view, but animating the brush used to paint the element enables you to be more selective about which portion of the element fades. For example, you could animate the opacity of a brush used to paint a button's background. This would cause the button's background to fade in and out of view, while leaving its text fully opaque.

Note:
Animating the Opacity of a Brush provides performance benefits over animating the Opacity property of an element.

In the following example, two buttons are animated so that they fade in and out of view. The Opacity of the first Button is animated from 1.0 to 0.0 over a Duration of five seconds. The second button is also animated, but the Opacity of the SolidColorBrush used to paint its Background is animated rather than the opacity of the entire button. When the example is run, the first button completely fades in and out of view, while only the background of the second button fades in and out of view. Its text and border remain fully opaque.

<!-- OpacityAnimationExample.xaml
     This example shows how to animate the opacity of objects, 
     making them fade in and out of view. -->
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  WindowTitle="Opacity Animation Example" Background="White">
  <StackPanel Margin="20">

    <!-- Clicking this button animates its opacity. -->
    <Button Name="opacityAnimatedButton">
      A Button
      <Button.Triggers>
        <EventTrigger RoutedEvent="Button.Click">
          <BeginStoryboard>
            <Storyboard>
              <DoubleAnimation 
                Storyboard.TargetName="opacityAnimatedButton"
                Storyboard.TargetProperty="(Button.Opacity)" 
                From="1" To="0" Duration="0:0:5" AutoReverse="True"  /> 
            </Storyboard>
          </BeginStoryboard>
        </EventTrigger>
      </Button.Triggers>
    </Button>

    <!-- Clicking this button animates the opacity of the brush
         used to paint its background. -->
    <Button>
      A Button
      <Button.Background>
        <SolidColorBrush x:Name="MyAnimatedBrush" Color="Orange" />
      </Button.Background>
      <Button.Triggers>
        <EventTrigger RoutedEvent="Button.Click">
          <BeginStoryboard>
            <Storyboard>
              <DoubleAnimation 
                Storyboard.TargetName="MyAnimatedBrush"
                Storyboard.TargetProperty="(Brush.Opacity)" 
                From="1" To="0" Duration="0:0:5" AutoReverse="True"  />  
            </Storyboard>
          </BeginStoryboard>
        </EventTrigger>
      </Button.Triggers>         
    </Button>
  </StackPanel>
</Page>

Code has been omitted from this example. The full sample also shows how to animate the opacity of a Color within a LinearGradientBrush. For the full sample, see the Animating the Opacity of an Element Sample.

More Code

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

.NET Framework

Reference

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