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Expander ControlTemplate Example

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Controls in Windows Presentation Foundation (WPF) have a ControlTemplate that contains the visual tree of that control. You can change the structure and appearance of a control by modifying the ControlTemplate of that control. There is no way to replace only part of the visual tree of a control; to change the visual tree of a control you must set the Template property of the control to its new and complete ControlTemplate.

This topic shows the ControlTemplate of the WPF Expander control.

This topic contains the following sections.

  • Prerequisites
  • Expander ControlTemplate Example
  • Related Topics

Prerequisites

To run the examples in this topic, you should understand how to write WPF applications. For more information, see Get Started Using Windows Presentation Foundation. You should also understand how styles are used in WPF. For more information, see Styling and Templating.

Expander ControlTemplate Example

While this example contains all of the elements that are defined in the ControlTemplate of an Expander by default, the specific values should be thought of as examples.

<ControlTemplate x:Key="ExpanderToggleButton" TargetType="ToggleButton">
  <Border
    Name="Border" 
    CornerRadius="2,0,0,0"
    Background="Transparent"
    BorderBrush="{StaticResource NormalBorderBrush}"
    BorderThickness="0,0,1,0">
    <Path 
      Name="Arrow"
      Fill="{StaticResource GlyphBrush}"
      HorizontalAlignment="Center"
      VerticalAlignment="Center"
      Data="M 0 0 L 4 4 L 8 0 Z"/>
  </Border>
  <ControlTemplate.Triggers>
    <Trigger Property="ToggleButton.IsMouseOver" Value="true">
      <Setter TargetName="Border" Property="Background"
              Value="{StaticResource DarkBrush}" />
    </Trigger>
    <Trigger Property="IsPressed" Value="true">
      <Setter TargetName="Border" Property="Background"
              Value="{StaticResource PressedBrush}" />
    </Trigger>
    <Trigger Property="IsChecked" Value="true">
      <Setter TargetName="Arrow" Property="Data"
              Value="M 0 4 L 4 0 L 8 4 Z" />
    </Trigger>
    <Trigger Property="IsEnabled" Value="False">
      <Setter TargetName="Border" Property="Background"
              Value="{StaticResource DisabledBackgroundBrush}" />
      <Setter TargetName="Border" Property="BorderBrush"
              Value="{StaticResource DisabledBorderBrush}" />
      <Setter Property="Foreground"
              Value="{StaticResource DisabledForegroundBrush}"/>
      <Setter TargetName="Arrow" Property="Fill"
              Value="{StaticResource DisabledForegroundBrush}" />
    </Trigger>
  </ControlTemplate.Triggers>
</ControlTemplate>

<Style TargetType="Expander">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="Expander">
        <Grid>
          <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Name="ContentRow" Height="0"/>
          </Grid.RowDefinitions>
          <Border 
            Name="Border" 
            Grid.Row="0" 
            Background="{StaticResource LightBrush}"
            BorderBrush="{StaticResource NormalBorderBrush}"
            BorderThickness="1" 
            CornerRadius="2,2,0,0" >
            <Grid>
              <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20" />
                <ColumnDefinition Width="*" />
              </Grid.ColumnDefinitions>
              <ToggleButton
                IsChecked="{Binding Path=IsExpanded,Mode=TwoWay,
                                    RelativeSource={RelativeSource TemplatedParent}}"
                OverridesDefaultStyle="True" 
                Template="{StaticResource ExpanderToggleButton}" 
                Background="{StaticResource NormalBrush}" />
              <ContentPresenter 
                Grid.Column="1"
                Margin="4" 
                ContentSource="Header" 
                RecognizesAccessKey="True" />
            </Grid>
          </Border>
          <Border 
            Name="Content" 
            Grid.Row="1" 
            Background="{StaticResource WindowBackgroundBrush}"
            BorderBrush="{StaticResource SolidBorderBrush}" 
            BorderThickness="1,0,1,1" 
            CornerRadius="0,0,2,2" >
            <ContentPresenter Margin="4" />
          </Border>
        </Grid>
        <ControlTemplate.Triggers>
          <Trigger Property="IsExpanded" Value="True">
            <Setter TargetName="ContentRow" Property="Height"
                    Value="{Binding ElementName=Content,Path=DesiredHeight}" />
          </Trigger>
          <Trigger Property="IsEnabled" Value="False">
            <Setter TargetName="Border" Property="Background"
                    Value="{StaticResource DisabledBackgroundBrush}" />
            <Setter TargetName="Border" Property="BorderBrush"
                    Value="{StaticResource DisabledBorderBrush}" />
            <Setter Property="Foreground"
                    Value="{StaticResource DisabledForegroundBrush}"/>
          </Trigger>

        </ControlTemplate.Triggers>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

The above example uses one or more of the following resources:

<!-- Fill Brushes -->

<LinearGradientBrush x:Key="NormalBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#CCC" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalNormalBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#CCC" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="LightBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalLightBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="DarkBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#AAA" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="PressedBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#BBB" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="0.1"/>
      <GradientStop Color="#EEE" Offset="0.9"/>
      <GradientStop Color="#FFF" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<SolidColorBrush x:Key="DisabledForegroundBrush" Color="#888" />

<SolidColorBrush x:Key="DisabledBackgroundBrush" Color="#EEE" />

<SolidColorBrush x:Key="WindowBackgroundBrush" Color="#FFF" />

<SolidColorBrush x:Key="SelectedBackgroundBrush" Color="#DDD" />

<!-- Border Brushes -->

<LinearGradientBrush x:Key="NormalBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#CCC" Offset="0.0"/>
      <GradientStop Color="#444" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalNormalBorderBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#CCC" Offset="0.0"/>
      <GradientStop Color="#444" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="DefaultedBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#777" Offset="0.0"/>
      <GradientStop Color="#000" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="PressedBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#444" Offset="0.0"/>
      <GradientStop Color="#888" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<SolidColorBrush x:Key="DisabledBorderBrush" Color="#AAA" />

<SolidColorBrush x:Key="SolidBorderBrush" Color="#888" />

<SolidColorBrush x:Key="LightBorderBrush" Color="#AAA" />

<!-- Miscellaneous Brushes -->
<SolidColorBrush x:Key="GlyphBrush" Color="#444" />

<SolidColorBrush x:Key="LightColorBrush" Color="#DDD" />

For the complete sample, see Styling with ControlTemplates Sample.

See Also

Concepts

Guidelines for Designing Stylable Controls

Other Resources

ControlTemplate Examples