Default ControlTemplate for Expander
I have blend, and can help you out. Here is what Blend generated for me.
<ResourceDictionaryxmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"><Style x:Key="ExpanderRightHeaderStyle" TargetType="{x:Type ToggleButton}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type ToggleButton}"> <Border Padding="{TemplateBinding Padding}"> <Grid Background="Transparent" SnapsToDevicePixels="False"> <Grid.RowDefinitions> <RowDefinition Height="19"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <Grid> <Grid.LayoutTransform> <TransformGroup> <TransformGroup.Children> <TransformCollection> <RotateTransform Angle="-90"/> </TransformCollection> </TransformGroup.Children> </TransformGroup> </Grid.LayoutTransform> <Ellipse x:Name="circle" HorizontalAlignment="Center" Height="19" Stroke="DarkGray" VerticalAlignment="Center" Width="19"/> <Path x:Name="arrow" Data="M 1,1.5 L 4.5,5 L 8,1.5" HorizontalAlignment="Center" SnapsToDevicePixels="false" Stroke="#666" StrokeThickness="2" VerticalAlignment="Center"/> </Grid> <ContentPresenter HorizontalAlignment="Center" Margin="0,4,0,0" Grid.Row="1" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Top"/> </Grid> </Border> <ControlTemplate.Triggers> <Trigger Property="IsChecked" Value="true"> <Setter Property="Data" TargetName="arrow" Value="M 1,4.5 L 4.5,1 L 8,4.5"/> </Trigger> <Trigger Property="IsMouseOver" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF3C7FB1"/> <Setter Property="Stroke" TargetName="arrow" Value="#222"/> </Trigger> <Trigger Property="IsPressed" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF526C7B"/> <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/> <Setter Property="Stroke" TargetName="arrow" Value="#FF003366"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter></Style><Style x:Key="ExpanderUpHeaderStyle" TargetType="{x:Type ToggleButton}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type ToggleButton}"> <Border Padding="{TemplateBinding Padding}"> <Grid Background="Transparent" SnapsToDevicePixels="False"> <Grid.ColumnDefinitions> <ColumnDefinition Width="19"/> <ColumnDefinition Width="*"/> </Grid.ColumnDefinitions> <Grid> <Grid.LayoutTransform> <TransformGroup> <TransformGroup.Children> <TransformCollection> <RotateTransform Angle="180"/> </TransformCollection> </TransformGroup.Children> </TransformGroup> </Grid.LayoutTransform> <Ellipse x:Name="circle" HorizontalAlignment="Center" Height="19" Stroke="DarkGray" VerticalAlignment="Center" Width="19"/> <Path x:Name="arrow" Data="M 1,1.5 L 4.5,5 L 8,1.5" HorizontalAlignment="Center" SnapsToDevicePixels="false" Stroke="#666" StrokeThickness="2" VerticalAlignment="Center"/> </Grid> <ContentPresenter Grid.Column="1" HorizontalAlignment="Left" Margin="4,0,0,0" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Center"/> </Grid> </Border> <ControlTemplate.Triggers> <Trigger Property="IsChecked" Value="true"> <Setter Property="Data" TargetName="arrow" Value="M 1,4.5 L 4.5,1 L 8,4.5"/> </Trigger> <Trigger Property="IsMouseOver" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF3C7FB1"/> <Setter Property="Stroke" TargetName="arrow" Value="#222"/> </Trigger> <Trigger Property="IsPressed" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF526C7B"/> <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/> <Setter Property="Stroke" TargetName="arrow" Value="#FF003366"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter></Style><Style x:Key="ExpanderLeftHeaderStyle" TargetType="{x:Type ToggleButton}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type ToggleButton}"> <Border Padding="{TemplateBinding Padding}"> <Grid Background="Transparent" SnapsToDevicePixels="False"> <Grid.RowDefinitions> <RowDefinition Height="19"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <Grid> <Grid.LayoutTransform> <TransformGroup> <TransformGroup.Children> <TransformCollection> <RotateTransform Angle="90"/> </TransformCollection> </TransformGroup.Children> </TransformGroup> </Grid.LayoutTransform> <Ellipse x:Name="circle" HorizontalAlignment="Center" Height="19" Stroke="DarkGray" VerticalAlignment="Center" Width="19"/> <Path x:Name="arrow" Data="M 1,1.5 L 4.5,5 L 8,1.5" HorizontalAlignment="Center" SnapsToDevicePixels="false" Stroke="#666" StrokeThickness="2" VerticalAlignment="Center"/> </Grid> <ContentPresenter HorizontalAlignment="Center" Margin="0,4,0,0" Grid.Row="1" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Top"/> </Grid> </Border> <ControlTemplate.Triggers> <Trigger Property="IsChecked" Value="true"> <Setter Property="Data" TargetName="arrow" Value="M 1,4.5 L 4.5,1 L 8,4.5"/> </Trigger> <Trigger Property="IsMouseOver" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF3C7FB1"/> <Setter Property="Stroke" TargetName="arrow" Value="#222"/> </Trigger> <Trigger Property="IsPressed" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF526C7B"/> <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/> <Setter Property="Stroke" TargetName="arrow" Value="#FF003366"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter></Style><Style x:Key="ExpanderHeaderFocusVisual"> <Setter Property="Control.Template"> <Setter.Value> <ControlTemplate> <Border> <Rectangle Margin="0" SnapsToDevicePixels="true" Stroke="Black" StrokeThickness="1" StrokeDashArray="1 2"/> </Border> </ControlTemplate> </Setter.Value> </Setter></Style><Style x:Key="ExpanderDownHeaderStyle" TargetType="{x:Type ToggleButton}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type ToggleButton}"> <Border Padding="{TemplateBinding Padding}"> <Grid Background="Transparent" SnapsToDevicePixels="False"> <Grid.ColumnDefinitions> <ColumnDefinition Width="19"/> <ColumnDefinition Width="*"/> </Grid.ColumnDefinitions> <Ellipse x:Name="circle" HorizontalAlignment="Center" Height="19" Stroke="DarkGray" VerticalAlignment="Center" Width="19"/> <Path x:Name="arrow" Data="M 1,1.5 L 4.5,5 L 8,1.5" HorizontalAlignment="Center" SnapsToDevicePixels="false" Stroke="#666" StrokeThickness="2" VerticalAlignment="Center"/> <ContentPresenter Grid.Column="1" HorizontalAlignment="Left" Margin="4,0,0,0" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Center"/> </Grid> </Border> <ControlTemplate.Triggers> <Trigger Property="IsChecked" Value="true"> <Setter Property="Data" TargetName="arrow" Value="M 1,4.5 L 4.5,1 L 8,4.5"/> </Trigger> <Trigger Property="IsMouseOver" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF3C7FB1"/> <Setter Property="Stroke" TargetName="arrow" Value="#222"/> </Trigger> <Trigger Property="IsPressed" Value="true"> <Setter Property="Stroke" TargetName="circle" Value="#FF526C7B"/> <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/> <Setter Property="Stroke" TargetName="arrow" Value="#FF003366"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter></Style><Style x:Key="ExpanderStyle1" TargetType="{x:Type Expander}"> <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/> <Setter Property="Background" Value="Transparent"/> <Setter Property="HorizontalContentAlignment" Value="Stretch"/> <Setter Property="VerticalContentAlignment" Value="Stretch"/> <Setter Property="BorderBrush" Value="Transparent"/> <Setter Property="BorderThickness" Value="1"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type Expander}"> <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" CornerRadius="3" SnapsToDevicePixels="true"> <DockPanel> <ToggleButton x:Name="HeaderSite" ContentTemplate="{TemplateBinding HeaderTemplate}" ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}" Content="{TemplateBinding Header}" DockPanel.Dock="Top" Foreground="{TemplateBinding Foreground}" FontWeight="{TemplateBinding FontWeight}" FocusVisualStyle="{StaticResource ExpanderHeaderFocusVisual}" FontStyle="{TemplateBinding FontStyle}" FontStretch="{TemplateBinding FontStretch}" FontSize="{TemplateBinding FontSize}" FontFamily="{TemplateBinding FontFamily}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" IsChecked="{Binding IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" MinWidth="0" MinHeight="0" Padding="{TemplateBinding Padding}" Style="{StaticResource ExpanderDownHeaderStyle}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/> <ContentPresenter x:Name="ExpandSite" DockPanel.Dock="Bottom" Focusable="false" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" Visibility="Collapsed" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> </DockPanel> </Border> <ControlTemplate.Triggers> <Trigger Property="IsExpanded" Value="true"> <Setter Property="Visibility" TargetName="ExpandSite" Value="Visible"/> </Trigger> <Trigger Property="ExpandDirection" Value="Right"> <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Right"/> <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Left"/> <Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderRightHeaderStyle}"/> </Trigger> <Trigger Property="ExpandDirection" Value="Up"> <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Top"/> <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Bottom"/> <Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderUpHeaderStyle}"/> </Trigger> <Trigger Property="ExpandDirection" Value="Left"> <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Left"/> <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Right"/> <Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderLeftHeaderStyle}"/> </Trigger> <Trigger Property="IsEnabled" Value="false"> <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter></Style><!-- Resource dictionary entries should be defined here. -->