扩展时在Wpf中更改ToggleButton for Expander

Question

I want to change the toggler of expander when I collapse and uncollapse. Which means, I want to place an image instead. Is there a simpler way to do that in XAML rather than building ypur own expander template?

Answer 1

Just edit existing template in Blend, which will create a full copy of the existing template, then style it however you'd like. Should be pretty simple once you have the full style template to mess around with (I've done it before).

Here's the full, default template for the Expander:

    <SolidColorBrush x:Key="Expander.MouseOver.Circle.Stroke" Color="#FF5593FF"/>
    <SolidColorBrush x:Key="Expander.MouseOver.Circle.Fill" Color="#FFF3F9FF"/>
    <SolidColorBrush x:Key="Expander.MouseOver.Arrow.Stroke" Color="#FF000000"/>
    <SolidColorBrush x:Key="Expander.Pressed.Circle.Stroke" Color="#FF3C77DD"/>
    <SolidColorBrush x:Key="Expander.Pressed.Circle.Fill" Color="#FFD9ECFF"/>
    <SolidColorBrush x:Key="Expander.Pressed.Arrow.Stroke" Color="#FF000000"/>
    <SolidColorBrush x:Key="Expander.Disabled.Circle.Stroke" Color="#FFBCBCBC"/>
    <SolidColorBrush x:Key="Expander.Disabled.Circle.Fill" Color="#FFE6E6E6"/>
    <SolidColorBrush x:Key="Expander.Disabled.Arrow.Stroke" Color="#FF707070"/>
    <SolidColorBrush x:Key="Expander.Static.Circle.Fill" Color="#FFFFFFFF"/>
    <SolidColorBrush x:Key="Expander.Static.Circle.Stroke" Color="#FF333333"/>
    <SolidColorBrush x:Key="Expander.Static.Arrow.Stroke" Color="#FF333333"/>
    <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" Fill="{StaticResource Expander.Static.Circle.Fill}" HorizontalAlignment="Center" Height="19" Stroke="{StaticResource Expander.Static.Circle.Stroke}" 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="{StaticResource Expander.Static.Arrow.Stroke}" 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="{StaticResource Expander.MouseOver.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.MouseOver.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.MouseOver.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Stroke}"/>
                            <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Pressed.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Disabled.Arrow.Stroke}"/>
                        </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" Fill="{StaticResource Expander.Static.Circle.Fill}" HorizontalAlignment="Center" Height="19" Stroke="{StaticResource Expander.Static.Circle.Stroke}" 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="{StaticResource Expander.Static.Arrow.Stroke}" 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="{StaticResource Expander.MouseOver.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.MouseOver.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.MouseOver.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Stroke}"/>
                            <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Pressed.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Disabled.Arrow.Stroke}"/>
                        </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" Fill="{StaticResource Expander.Static.Circle.Fill}" HorizontalAlignment="Center" Height="19" Stroke="{StaticResource Expander.Static.Circle.Stroke}" 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="{StaticResource Expander.Static.Arrow.Stroke}" 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="{StaticResource Expander.MouseOver.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.MouseOver.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.MouseOver.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Stroke}"/>
                            <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Pressed.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Disabled.Arrow.Stroke}"/>
                        </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" Fill="{StaticResource Expander.Static.Circle.Fill}" HorizontalAlignment="Center" Height="19" Stroke="{StaticResource Expander.Static.Circle.Stroke}" 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="{StaticResource Expander.Static.Arrow.Stroke}" 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="{StaticResource Expander.MouseOver.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.MouseOver.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.MouseOver.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Stroke}"/>
                            <Setter Property="StrokeThickness" TargetName="circle" Value="1.5"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Pressed.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Pressed.Arrow.Stroke}"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Stroke" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Stroke}"/>
                            <Setter Property="Fill" TargetName="circle" Value="{StaticResource Expander.Disabled.Circle.Fill}"/>
                            <Setter Property="Stroke" TargetName="arrow" Value="{StaticResource Expander.Disabled.Arrow.Stroke}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style 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>

Each style used by the main template defines an ellipse and a path that you can change to instead use an Image with a bindable source or whatever you want to do.