wpf An Introduction to WPF Styles Button Style DoubleAnimation

Example

The following Window has been created:

<Window x:Class="WPF_Style_Example.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" ResizeMode="NoResize"
    Title="MainWindow"
    Height="150" Width="250">
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition/>
    </Grid.RowDefinitions>
    <Button Margin="5" Content="Button 1" Width="200"/>
    <Button Margin="5" Grid.Row="1" Content="Button 2" Width="200"/>
</Grid>

A style (created in App.xaml) has been applied to the buttons, which animates the width from 200 to 100 when the mouse enters the control and from 100 to 200 when it leaves:

<Style TargetType="{x:Type Button}">
    <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
    <Setter Property="Background" Value="{StaticResource Button.Static.Background}"/>
    <Setter Property="BorderBrush" Value="{StaticResource Button.Static.Border}"/>
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
    <Setter Property="BorderThickness" Value="1"/>
    <Setter Property="HorizontalContentAlignment" Value="Center"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="Padding" Value="1"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type Button}">
                <Grid Background="White">
                    <Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
                        <ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </Border>
                </Grid>
                <ControlTemplate.Triggers>
                    <EventTrigger RoutedEvent="MouseEnter">
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation To="100" From="200" Storyboard.TargetProperty="Width" Storyboard.TargetName="border" Duration="0:0:0.25"/>
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
                    <EventTrigger RoutedEvent="MouseLeave">
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation To="200" From="100" Storyboard.TargetProperty="Width" Storyboard.TargetName="border" Duration="0:0:0.25"/>
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
                    <Trigger Property="IsDefaulted" Value="true">
                        <Setter Property="BorderBrush" TargetName="border" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                    </Trigger>
                    <Trigger Property="IsMouseOver" Value="true">
                        <Setter Property="Background" TargetName="border" Value="{StaticResource Button.MouseOver.Background}"/>
                        <Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.MouseOver.Border}"/>
                    </Trigger>
                    <Trigger Property="IsPressed" Value="true">
                        <Setter Property="Background" TargetName="border" Value="{StaticResource Button.Pressed.Background}"/>
                        <Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Pressed.Border}"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Background" TargetName="border" Value="{StaticResource Button.Disabled.Background}"/>
                        <Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Disabled.Border}"/>
                        <Setter Property="TextElement.Foreground" TargetName="contentPresenter" Value="{StaticResource Button.Disabled.Foreground}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>