wpf 使用了 template 了的 combobox 中，displaymemberpath 有 bug，仅在 popup 中生效

需求是：仅想改变combobox的默认样式，所以 template 是直接在属性窗口点击转化为本地值的。

using System.Collections.Generic;
using System.Windows;

namespace WpfApp2 {
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
            var list = new List<MyClass> { new MyClass { Name = "lwieru" } };
            a.ItemsSource = aa.ItemsSource = list;
            a.SelectedItem = aa.SelectedItem = list[0];
        }
        class MyClass {
            public string Name { get; set; }
        }
    }
}

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero2"
    x:Class="WpfApp2.MainWindow">
    <StackPanel>
        <ComboBox x:Name="a" DisplayMemberPath="Name"/>
        <ComboBox x:Name="aa" DisplayMemberPath="Name">
            <ComboBox.Template>
                <ControlTemplate TargetType="{x:Type ComboBox}">
                    <Grid x:Name="templateRoot" SnapsToDevicePixels="True">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition MinWidth="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" Width="0"/>
                        </Grid.ColumnDefinitions>
                        <Popup x:Name="PART_Popup" AllowsTransparency="True" Grid.ColumnSpan="2" IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
                            <Themes:SystemDropShadowChrome x:Name="shadow" Color="Transparent" MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{Binding ActualWidth, ElementName=templateRoot}">
                                <Border x:Name="DropDownBorder" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}">
                                    <ScrollViewer x:Name="DropDownScrollViewer">
                                        <Grid x:Name="grid" RenderOptions.ClearTypeHint="Enabled">
                                            <Canvas x:Name="canvas" HorizontalAlignment="Left" Height="0" VerticalAlignment="Top" Width="0">
                                                <Rectangle x:Name="OpaqueRect" Fill="{Binding Background, ElementName=DropDownBorder}" Height="{Binding ActualHeight, ElementName=DropDownBorder}" Width="{Binding ActualWidth, ElementName=DropDownBorder}"/>
                                            </Canvas>
                                            <ItemsPresenter x:Name="ItemsPresenter" KeyboardNavigation.DirectionalNavigation="Contained" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                                        </Grid>
                                    </ScrollViewer>
                                </Border>
                            </Themes:SystemDropShadowChrome>
                        </Popup>
                        <ToggleButton x:Name="toggleButton" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.ColumnSpan="2" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
                            <ToggleButton.Style>
                                <Style TargetType="{x:Type ToggleButton}">
                                    <Setter Property="OverridesDefaultStyle" Value="True"/>
                                    <Setter Property="IsTabStop" Value="False"/>
                                    <Setter Property="Focusable" Value="False"/>
                                    <Setter Property="ClickMode" Value="Press"/>
                                    <Setter Property="Template">
                                        <Setter.Value>
                                            <ControlTemplate TargetType="{x:Type ToggleButton}">
                                                <Border x:Name="templateRoot" BorderBrush="#FFACACAC" BorderThickness="{TemplateBinding BorderThickness}" SnapsToDevicePixels="True">
                                                    <Border.Background>
                                                        <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                                                            <GradientStop Color="#FFF0F0F0" Offset="0"/>
                                                            <GradientStop Color="#FFE5E5E5" Offset="1"/>
                                                        </LinearGradientBrush>
                                                    </Border.Background>
                                                    <Border x:Name="splitBorder" BorderBrush="Transparent" BorderThickness="1" HorizontalAlignment="Right" Margin="0" SnapsToDevicePixels="True" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}">
                                                        <Path x:Name="Arrow" Data="F1M0,0L2.667,2.66665 5.3334,0 5.3334,-1.78168 2.6667,0.88501 0,-1.78168 0,0z" Fill="#FF606060" HorizontalAlignment="Center" Margin="0" VerticalAlignment="Center"/>
                                                    </Border>
                                                </Border>
                                                <ControlTemplate.Triggers>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="true"/>
                                                            <Condition Binding="{Binding IsMouseOver, RelativeSource={RelativeSource Self}}" Value="false"/>
                                                            <Condition Binding="{Binding IsPressed, RelativeSource={RelativeSource Self}}" Value="false"/>
                                                            <Condition Binding="{Binding IsEnabled, RelativeSource={RelativeSource Self}}" Value="true"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot" Value="White"/>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FFABADB3"/>
                                                        <Setter Property="Background" TargetName="splitBorder" Value="Transparent"/>
                                                        <Setter Property="BorderBrush" TargetName="splitBorder" Value="Transparent"/>
                                                    </MultiDataTrigger>
                                                    <Trigger Property="IsMouseOver" Value="True">
                                                        <Setter Property="Fill" TargetName="Arrow" Value="Black"/>
                                                    </Trigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsMouseOver, RelativeSource={RelativeSource Self}}" Value="true"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="false"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot">
                                                            <Setter.Value>
                                                                <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                                                                    <GradientStop Color="#FFECF4FC" Offset="0"/>
                                                                    <GradientStop Color="#FFDCECFC" Offset="1"/>
                                                                </LinearGradientBrush>
                                                            </Setter.Value>
                                                        </Setter>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FF7EB4EA"/>
                                                    </MultiDataTrigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsMouseOver, RelativeSource={RelativeSource Self}}" Value="true"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="true"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot" Value="White"/>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FF7EB4EA"/>
                                                        <Setter Property="Background" TargetName="splitBorder">
                                                            <Setter.Value>
                                                                <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                                                                    <GradientStop Color="#FFEBF4FC" Offset="0"/>
                                                                    <GradientStop Color="#FFDCECFC" Offset="1"/>
                                                                </LinearGradientBrush>
                                                            </Setter.Value>
                                                        </Setter>
                                                        <Setter Property="BorderBrush" TargetName="splitBorder" Value="#FF7EB4EA"/>
                                                    </MultiDataTrigger>
                                                    <Trigger Property="IsPressed" Value="True">
                                                        <Setter Property="Fill" TargetName="Arrow" Value="Black"/>
                                                    </Trigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsPressed, RelativeSource={RelativeSource Self}}" Value="true"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="false"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot">
                                                            <Setter.Value>
                                                                <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                                                                    <GradientStop Color="#FFDAECFC" Offset="0"/>
                                                                    <GradientStop Color="#FFC4E0FC" Offset="1"/>
                                                                </LinearGradientBrush>
                                                            </Setter.Value>
                                                        </Setter>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FF569DE5"/>
                                                    </MultiDataTrigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsPressed, RelativeSource={RelativeSource Self}}" Value="true"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="true"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot" Value="White"/>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FF569DE5"/>
                                                        <Setter Property="Background" TargetName="splitBorder">
                                                            <Setter.Value>
                                                                <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                                                                    <GradientStop Color="#FFDAEBFC" Offset="0"/>
                                                                    <GradientStop Color="#FFC4E0FC" Offset="1"/>
                                                                </LinearGradientBrush>
                                                            </Setter.Value>
                                                        </Setter>
                                                        <Setter Property="BorderBrush" TargetName="splitBorder" Value="#FF569DE5"/>
                                                    </MultiDataTrigger>
                                                    <Trigger Property="IsEnabled" Value="False">
                                                        <Setter Property="Fill" TargetName="Arrow" Value="#FFBFBFBF"/>
                                                    </Trigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsEnabled, RelativeSource={RelativeSource Self}}" Value="false"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="false"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot" Value="#FFF0F0F0"/>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FFD9D9D9"/>
                                                    </MultiDataTrigger>
                                                    <MultiDataTrigger>
                                                        <MultiDataTrigger.Conditions>
                                                            <Condition Binding="{Binding IsEnabled, RelativeSource={RelativeSource Self}}" Value="false"/>
                                                            <Condition Binding="{Binding IsEditable, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="true"/>
                                                        </MultiDataTrigger.Conditions>
                                                        <Setter Property="Background" TargetName="templateRoot" Value="White"/>
                                                        <Setter Property="BorderBrush" TargetName="templateRoot" Value="#FFBFBFBF"/>
                                                        <Setter Property="Background" TargetName="splitBorder" Value="Transparent"/>
                                                        <Setter Property="BorderBrush" TargetName="splitBorder" Value="Transparent"/>
                                                    </MultiDataTrigger>
                                                </ControlTemplate.Triggers>
                                            </ControlTemplate>
                                        </Setter.Value>
                                    </Setter>
                                </Style>
                            </ToggleButton.Style>
                        </ToggleButton>
                        <ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" Content="{TemplateBinding SelectionBoxItem}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" IsHitTestVisible="False" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="HasDropShadow" SourceName="PART_Popup" Value="True">
                            <Setter Property="Margin" TargetName="shadow" Value="0,0,5,5"/>
                            <Setter Property="Color" TargetName="shadow" Value="#71000000"/>
                        </Trigger>
                        <Trigger Property="HasItems" Value="False">
                            <Setter Property="Height" TargetName="DropDownBorder" Value="95"/>
                        </Trigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsGrouping" Value="True"/>
                                <Condition Property="VirtualizingPanel.IsVirtualizingWhenGrouping" Value="False"/>
                            </MultiTrigger.Conditions>
                            <Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
                        </MultiTrigger>
                        <Trigger Property="CanContentScroll" SourceName="DropDownScrollViewer" Value="False">
                            <Setter Property="Canvas.Top" TargetName="OpaqueRect" Value="{Binding VerticalOffset, ElementName=DropDownScrollViewer}"/>
                            <Setter Property="Canvas.Left" TargetName="OpaqueRect" Value="{Binding HorizontalOffset, ElementName=DropDownScrollViewer}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </ComboBox.Template>
        </ComboBox>
    </StackPanel>
</Window>