ボタンには次の XAML スタイルがあります。
<Style TargetType="{x:Type Button}">
<Setter Property="VerticalContentAlignment" Value="Center" />
<Setter Property="FontFamily" Value="Calibri" />
<Setter Property="Foreground" Value="White" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="BtnBorder" Width="{TemplateBinding ActualWidth}" Height="{TemplateBinding ActualHeight}" CornerRadius="5" VerticalAlignment="Center" BorderBrush="White" BorderThickness="0" ClipToBounds="True" HorizontalAlignment="Center">
<Grid Width="{Binding ElementName=BtnBorder, Path=ActualWidth}">
<Rectangle Name="BtnRect" RadiusX="6" RadiusY="5" Opacity="0.2" Fill="White" />
<Rectangle x:Name="progressIndicator" Width="0" HorizontalAlignment="Left" RadiusX="8" RadiusY="8" Margin="1">
<Rectangle.Fill>
<LinearGradientBrush StartPoint="0,0.5" EndPoint="1,0.5">
<GradientStop Color="Transparent" Offset="0" />
<GradientStop Color="#88FFFFFF" Offset="0.945" />
<GradientStop Color="White" Offset="1" />
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" x:Name="BtnCP" />
</Grid>
</Border>
<ControlTemplate.Triggers>
<EventTrigger RoutedEvent="Mouse.MouseEnter">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName="BtnRect" Storyboard.TargetProperty="Opacity" From="0.25" To="0.5" Duration="0:0:0.2" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<EventTrigger RoutedEvent="Mouse.MouseLeave">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName="BtnRect" Storyboard.TargetProperty="Opacity" From="0.5" To="0.25" Duration="0:0:0.5" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<Trigger Property="IsPressed" Value="True">
<Setter TargetName="BtnBorder" Property="BorderThickness" Value="1.3" />
<Trigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName="progressIndicator" Storyboard.TargetProperty="Width" From="0" To="300" Duration="0:0:5" AutoReverse="True" RepeatBehavior="5x" />
</Storyboard>
</BeginStoryboard>
</Trigger.EnterActions>
</Trigger>
<Trigger Property="IsFocused" Value="True">
<Setter TargetName="BtnBorder" Property="BorderThickness" Value="1.5,0,1.5,0" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsFocused" Value="True" />
<Condition Property="IsPressed" Value="True" />
</MultiTrigger.Conditions>
<Setter TargetName="BtnBorder" Property="BorderThickness" Value="1.3" />
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
ボタンをクリックしたときにコードビハインドを使用して、ボタンの Rectangle プロパティのアニメーションを制御するにはどうすればよいですか。「progressIndicator」という名前の Rectangle は、ユーザーがボタンをクリックすると、アニメーションによって幅が大きくなります。