我在网站上看了好几个问题，但似乎找不到答案。
我有一个ComboBox。它之前一直工作得很好。后来我决定需要彻底改变它的外观，于是我创建了默认ComboBox模板的一个副本（这是一个完全的副本，没有修改）：
<ControlTemplate x:Key="ComboBoxControlTemplate2" TargetType="{x:Type ComboBox}">
<Grid x:Name="MainGrid" 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, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
<Microsoft_Windows_Themes:SystemDropShadowChrome x:Name="Shdw" Color="Transparent" MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{Binding ActualWidth, ElementName=MainGrid}">
<Border x:Name="DropDownBorder" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}">
<ScrollViewer x:Name="DropDownScrollViewer">
<Grid RenderOptions.ClearTypeHint="Enabled">
<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>
</Microsoft_Windows_Themes:SystemDropShadowChrome>
</Popup>
<ToggleButton BorderBrush="{TemplateBinding BorderBrush}" 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}">
<Microsoft_Windows_Themes:ButtonChrome x:Name="Chrome" BorderBrush="{TemplateBinding BorderBrush}" Background="{TemplateBinding Background}" RenderMouseOver="{TemplateBinding IsMouseOver}" RenderPressed="{TemplateBinding IsPressed}" SnapsToDevicePixels="True">
<Grid HorizontalAlignment="Right" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}">
<Path x:Name="Arrow" Data="M0,0L3.5,4 7,0z" Fill="Black" HorizontalAlignment="Center" Margin="3,1,0,0" VerticalAlignment="Center"/>
</Grid>
</Microsoft_Windows_Themes:ButtonChrome>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter Property="RenderPressed" TargetName="Chrome" Value="True"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Fill" TargetName="Arrow" Value="#FFAFAFAF"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ToggleButton.Style>
</ToggleButton>
<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="Shdw" Value="0,0,5,5"/>
<Setter Property="Color" TargetName="Shdw" Value="#71000000"/>
</Trigger>
<Trigger Property="HasItems" Value="False">
<Setter Property="Height" TargetName="DropDownBorder" Value="95"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
<Setter Property="Background" Value="#FFF4F4F4"/>
</Trigger>
<Trigger Property="IsGrouping" Value="True">
<Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
</Trigger>
<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>
我的研究和实验让我相信，问题在于我的新模板没有利用 DisplayMemberPath 属性。我尝试通过覆盖 OnDisplayMemberPathChanged 方法来设置 ItemTemplate，但这会在我从列表中选择一个项目时导致错误。
我还看到有人通过 XAML 设置 ItemTemplate，但我有数百个组合框，我不想这样做。
是否有一些方法可以在我的 ControlTemplate 中利用 DisplayMemberPath 属性，或者在派生控件中运行一些代码以实现我想要的结果？
ContentPresenter是选定项目的关键组件，因此如果有错误应该在那里，然后我只需要将其与你的进行比较，就可以发现这个属性缺失了。我还测试了删除该属性的效果，并如预期地只显示了类型名称。 - H.B.