wpf - ComboBox 的自定义模板忽略 DisplayMemberPath 的使用

Question

所以我在网站上浏览了几个问题，但似乎找不到答案。

我有一个 ComboBox .它工作得很好。我决定需要大修外观，所以我创建了默认 ComboBox 模板的副本(这是一个直接副本，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>

现在，当我从我的列表(它是 POCO 的集合)中选择一个项目时，它会显示命名空间和类名，而不是它应该显示的值。

我的研究和实验让我相信问题在于我的新模板没有使用 DisplayMemberPath属性(property)。我试图设置一个 ItemTemplate通过覆盖 OnDisplayMemberPathChanged方法，但是当我从列表中选择一个项目时会导致错误。

我也看到有人设置了 ItemTemplate通过 XAML，但我有数百个组合框，我不想这样做。

有什么方法可以利用 DisplayMemberPath我的 ControlTemplate 中的属性，或者我可以在派生控件中运行的一些代码来实现我想要的结果？

Answer 1

这不是一个精确的副本，这个元素中缺少一个关键的东西:

<ContentPresenter ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
        Content="{TemplateBinding SelectionBoxItem}"
        ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}"
        HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
        IsHitTestVisible="False"
        Margin="{TemplateBinding Padding}"
        SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
        VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />

也许你不小心删除了它，即:

 ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"

如果你没有这个设置 DisplayMemberPath将不起作用，因为 ComboBox使用模板选择器在模板之间进行选择(如您可以使用 ItemTemplate 或 DisplayMemberPath )。