WPF Diagram Designer - Part 3

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

  <ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="Shared.xaml" />
  </ResourceDictionary.MergedDictionaries>

  <!-- SimpleStyles: Expander -->

  <ControlTemplate x:Key="ExpanderToggleButton" TargetType="ToggleButton">
    <Border
      Name="Border" 
      CornerRadius="2,0,0,0"
      Background="Transparent"
      BorderBrush="{StaticResource NormalBorderBrush}"
      BorderThickness="0,0,0,0">
      <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="FontFamily" Value="SegoeUI"/>
    <Setter Property="FontSize" Value="12"/>
    <Setter Property="Foreground" Value="#4C4C4C"/>
    <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>
</ResourceDictionary>