继续聊WPF——Expander控件（2）

上一篇文章简单说了一下Expander控件，本文将编写一个自义模板的Expander控件，如下图所示：
<Window x:Class="Expander_Sample2.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Window.Resources>
        <!--
        ToogleButton的模板，
        因为要进和状态切换，故要用到ToggleButton控件
        -->
        <ControlTemplate x:Key="ToggleButtonTemp" TargetType="{x:Type ToggleButton}">
            <Border x:Name="bd"
                    BorderThickness="1"
                    CornerRadius="1,1,1,1">
                <Border.Background>
                    <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
                        <GradientStop Color="LightGray" Offset="0"/>
                        <GradientStop Color="White" Offset="1"/>
                    </LinearGradientBrush>
                </Border.Background>
                <Border.BorderBrush>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
                        <GradientStop Color="Black" Offset="0"/>
                        <GradientStop Color="Gray" Offset="1"/>
                    </LinearGradientBrush>
                </Border.BorderBrush>
                <Path Margin="2,2,2,2" Fill="Black" x:Name="p"
                      Data="M 0,0 L 4,5 L8,0 Z"
                      HorizontalAlignment="Center"
                      VerticalAlignment="Center"/>
            </Border>
            <ControlTemplate.Triggers>
                <Trigger Property="IsMouseOver" Value="True">
                    <Setter TargetName="bd" Property="Background">
                        <Setter.Value>
                            <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
                                <GradientStop Color="LightGreen" Offset="0"/>
                                <GradientStop Color="White" Offset="1"/>
                            </LinearGradientBrush>
                        </Setter.Value>
                    </Setter>
                </Trigger>
                <Trigger Property="IsChecked" Value="True">
                    <Setter TargetName="p" Property="Data"
                                Value="M0,5 L8,5 L4,0 Z"/>
                </Trigger>
                <Trigger Property="IsEnabled" Value="True">
                    <Setter TargetName="bd" Property="BorderBrush" Value="Gray"/>
                    <Setter TargetName="p" Property="Fill" Value="Gray"/>
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>
        <!--
            Expnder的样式
        -->
        <Style TargetType="{x:Type Expander}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Expander}">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="auto"/>
                                <RowDefinition x:Name="gr" Height="0"/>
                            </Grid.RowDefinitions>
                            <BulletDecorator Background="DarkTurquoise" Grid.Row="0" VerticalAlignment="Center" >
                                <BulletDecorator.Bullet>
                                    <ToggleButton Margin="1,1,1,1"  Height="18" Width="18" Template="{StaticResource ToggleButtonTemp}"
                                                  IsChecked="{Binding Path=IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
                                                  OverridesDefaultStyle="True"/>
                                </BulletDecorator.Bullet>
                                <ContentPresenter HorizontalAlignment="Center" Margin="1,1,1,1" ContentSource="Header"/>
                            </BulletDecorator>
                            <Border x:Name="scv" Background="LightGray" BorderThickness="1" BorderBrush="Black" Grid.Row="1" >
                                <ContentPresenter Margin="0" ContentSource="Content"/>
                            </Border>
                        </Grid>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsExpanded" Value="True">
                                <Setter TargetName="gr" Property="Height" Value="{Binding Path=DesiredSize/Height,ElementName=scv}"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>
    <Grid>
        <Expander Margin="10,10" Height="210" Width="130" OverridesDefaultStyle="True">
            <Expander.Header>
                <TextBlock Text="相见恨晚" FontWeight="Bold" FontSize="16"/>
            </Expander.Header>
            <TextBlock TextWrapping="Wrap">
                如果相见不会太晚，我们就不会悲伤，和你堂堂的手牵手，过得好简单，
                若我有天不见了，或许你会比较快乐，虽然有万般舍不得，也不愿看你难割舍 
                若我有天不在了。请你原谅我的困扰，虽然你给我的不算少，只是我没福气要就算是完美。
            </TextBlock>
        </Expander>
    </Grid>
</Window>