Page.xaml

<UserControl x:Class="objectanimationusingkeyframes.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Width="400" Height="300">
    <StackPanel>
        <TextBlock Margin="10" TextWrapping="Wrap">This sample uses the ObjectAnimationUsingKeyFrames class to animate the Fill property of a Rectangle.</TextBlock>
        <!-- <SnippetObjectanimationusingkeyframes> -->
    <StackPanel>
        <StackPanel.Resources>
            <Storyboard x:Name="myStoryboard">

                <!-- ObjectAnimationUsingKeyFrames is used to animate properties that take
             an object as a value. This animation lasts for 4 seconds using 3 KeyFrames which
             swap different brush objects at regular intervals, making the background of the Page
             change. -->
                <ObjectAnimationUsingKeyFrames
             Storyboard.TargetName="animatedRectangle"
             Storyboard.TargetProperty="Fill"
             Duration="0:0:4" RepeatBehavior="Forever">
                    <ObjectAnimationUsingKeyFrames.KeyFrames>

                        <!-- Note: Only discrete interpolation (DiscreteObjectKeyFrame) is available for 
                    use with ObjectAnimationUsingKeyFrames which merely swaps objects according to
                    a specified timeline. Other types of interpolation are too problematic to apply
                    to objects.  -->
                        <!-- Using a DiscreteObjectKeyFrame, the Fill property of the Rectangle suddenly  
                    changes to a LinearGradientBrush after the first two seconds of the animation. -->
                        <DiscreteObjectKeyFrame KeyTime="0:0:2">
                            <DiscreteObjectKeyFrame.Value>
                                <LinearGradientBrush>
                                    <LinearGradientBrush.GradientStops>
                                        <GradientStop Color="Yellow" Offset="0.0" />
                                        <GradientStop Color="Orange" Offset="0.5" />
                                        <GradientStop Color="Red" Offset="1.0" />
                                    </LinearGradientBrush.GradientStops>
                                </LinearGradientBrush>
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>

                        <!-- After the third second of the animation, the Fill property is suddenly changed 
                    to a different LinearGradientBrush which remains until the end of the animation 
                    (4 seconds total). -->
                        <DiscreteObjectKeyFrame KeyTime="0:0:3">
                            <DiscreteObjectKeyFrame.Value>
                                <LinearGradientBrush>
                                    <LinearGradientBrush.GradientStops>
                                        <GradientStop Color="White" Offset="0.0" />
                                        <GradientStop Color="MediumBlue" Offset="0.5" />
                                        <GradientStop Color="Black" Offset="1.0" />
                                    </LinearGradientBrush.GradientStops>
                                </LinearGradientBrush>
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>

                    </ObjectAnimationUsingKeyFrames.KeyFrames>
                </ObjectAnimationUsingKeyFrames>
            </Storyboard>
        </StackPanel.Resources>

        <!-- The Fill property of this rectangle is animated. -->
        <Rectangle x:Name="animatedRectangle" Loaded="Rectangle_Loaded" Width="300" Height="300" />

    </StackPanel>
    <!-- </SnippetObjectanimationusingkeyframes> -->
    </StackPanel>
</UserControl>