<Window.Resources>
    <DataTemplate x:Key="DefaultTemplate">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="Default: "/>
            <TextBlock Text="{Binding}"/>
        </StackPanel>        
    </DataTemplate>
    <DataTemplate x:Key="SpecialTemplate">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="Special: "/>
            <TextBlock Text="{Binding}"/>
        </StackPanel>
    </DataTemplate>
</Window.Resources>

<Grid>
    <Button 
        x:Name="TestButton" 
        Content="Test" 
        ContentTemplate="{StaticResource DefaultTemplate}"/>
</Grid>

• MouseOver
• MouseLeft

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();

        this.TestButton.MouseMove += 
            new MouseEventHandler(TestButton_MouseMove);
        this.TestButton.MouseLeave += 
            new MouseEventHandler(TestButton_MouseLeave);
    }

    private void TestButton_MouseMove(
        object sender, 
        MouseEventArgs e)
    {
        TestButton.ContentTemplate = 
            this.FindResource("SpecialTemplate") as DataTemplate;
    }

    private void TestButton_MouseLeave(
        object sender, 
        MouseEventArgs e)
    {
        TestButton.ContentTemplate = 
            this.FindResource("DefaultTemplate") as DataTemplate;
    }
}

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:demo="clr-namespace:WpfNamespaceDemo.Lib;assembly=WpfNamespace.Lib"

[assembly: XmlnsDefinition(
    "http://www.norberteder.com/2008/wpf", 
    "WpfNamespaceDemo")]

xmlns:local="http://www.norberteder.com/2008/wpf"

• The Properties window now contains the Events tab. The Events tab lets you create events, assign events, and review events.
• The Properties window now includes a category sort option and an alphabetical sort option to allow for faster property location.
• Code changes have been made to the XAML Refactor/Rename definition and to the Go to definition. These changes allow XAML rename operations to occur automatically. Additionally, you can navigate the XAML definition by pressing F12.
• You can now drag controls or create controls from the toolbox in XAML view or in Design view. You can do this even if you use a split view configuration.
• Snaplines are now implemented for control margins. This lets the designer control a fixed distance from other controls, from container edges, or from gridlines.
• Tab controls now support TabItem activation and TabItem design. To do this, click the tab that you want to design.
• The Expander control now expands conditionally based on what is selected. You can design the contents of the Expander control at design time with affecting the IsExpanded attribute of the runtime.

<Window.Resources>
    <Style TargetType="Button">
        <Setter Property="SnapsToDevicePixels" Value="true"/>
        <Setter Property="OverridesDefaultStyle" Value="true"/>
        <Setter Property="MinHeight" Value="0"/>
        <Setter Property="MinWidth" Value="75"/>
        <Setter Property="Margin" Value="10"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Button">
                    <Border x:Name="Border" 
                            Background="Beige"  
                            CornerRadius="2" 
                            BorderThickness="1" 
                            BorderBrush="Brown">
                        <ContentPresenter 
                            Margin="2" 
                            HorizontalAlignment="Center" 
                            VerticalAlignment="Center" 
                            RecognizesAccessKey="True"/>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsVisible" Value="false">
                            <Setter Property="Height" Value="0"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<StackPanel>
    <Button x:Name="Button1" 
            Content="Button1"/>
    <Button x:Name="Button2" 
            Content="Button2"/>
    <Button x:Name="Button3" 
            Content="Button3"/>
    <Button x:Name="SetButton" 
            Content="Toggle Button1 Un/Visible" 
            Click="SetButton_Click" />
    <Button x:Name="CheckButton" 
            Content="Check Height" 
            Click="CheckButton_Click"/>
</StackPanel>

private void SetButton_Click(object sender, RoutedEventArgs e)
{
    if (Button2.Visibility == Visibility.Visible)
        Button2.Visibility = Visibility.Hidden;
    else
        Button2.Visibility = Visibility.Visible;
}

<Trigger Property="IsVisible" Value="false">
    <Setter Property="Height" Value="0"/>
    <Setter Property="Margin" Value="0"/>
</Trigger>