更新2011-11-14

Update 2011-11-14

我最近再次遇到同样的要求，我不是很满意下面发布的解决方案。这是一个更好的方式来获得相同的行为，而不重新模板 ComboBoxItem 。它使用 DataTemplateSelector

I recently came upon the same requirement again and I wasn't very happy with the solution I posted below. Here is a nicer way to get the same behavior without re-templating the ComboBoxItem. It uses a DataTemplateSelector

首先，指定正则 DataTemplate ， ComboBox $ c>的资源中的下拉菜单 DataTemplate 和 ComboBoxItemTemplateSelector $ c>。然后引用 ComboBoxItemTemplateSelector 作为 DynamicResource ，用于 ItemTemplateSelector p>



First, specify the regular DataTemplate, the dropdown DataTemplate and the ComboBoxItemTemplateSelector in the resources for the ComboBox. Then reference the ComboBoxItemTemplateSelector as a DynamicResource for ItemTemplateSelector

<ComboBox ...
          ItemTemplateSelector="{DynamicResource itemTemplateSelector}">
    <ComboBox.Resources>
        <DataTemplate x:Key="selectedTemplate">
            <TextBlock Text="{Binding Path=ShortDescription}"/>
        </DataTemplate>
        <DataTemplate x:Key="dropDownTemplate">
            <TextBlock Text="{Binding Path=FullDescription}"/>
        </DataTemplate>
        <local:ComboBoxItemTemplateSelector
            x:Key="itemTemplateSelector"
            SelectedTemplate="{StaticResource selectedTemplate}"
            DropDownTemplate="{StaticResource dropDownTemplate}"/>
    </ComboBox.Resources>
</ComboBox>

ComboBoxItemTemplateSelector 检查容器是否为子 ComboBoxItem ，如果是，那么我们正在处理一个下拉项，否则它是 ComboBox 。

ComboBoxItemTemplateSelector checks if the container is the child of a ComboBoxItem, if it is, then we are dealing with a dropdown item, otherwise it is the item in the ComboBox.

public class ComboBoxItemTemplateSelector : DataTemplateSelector
{
    public DataTemplate DropDownTemplate
    {
        get;
        set;
    }
    public DataTemplate SelectedTemplate
    {
        get;
        set;
    }
    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        ComboBoxItem comboBoxItem = VisualTreeHelpers.GetVisualParent<ComboBoxItem>(container);
        if (comboBoxItem != null)
        {
            return DropDownTemplate;
        }
        return SelectedTemplate;
    }
}

public static T GetVisualParent<T>(object childObject) where T : Visual
{
    DependencyObject child = childObject as DependencyObject;
    while ((child != null) && !(child is T))
    {
        child = VisualTreeHelper.GetParent(child);
    }
    return child as T;
}

旧解决方案模拟 ComboBoxItem

<SolidColorBrush x:Key="SelectedBackgroundBrush" Color="#DDD" />
<SolidColorBrush x:Key="DisabledForegroundBrush" Color="#888" />

<ControlTemplate x:Key="FullDescriptionTemplate" TargetType="ComboBoxItem">
    <Border Name="Border" Padding="2" SnapsToDevicePixels="true">
        <StackPanel>
            <TextBlock Text="{Binding Path=FullDescription}"/>
        </StackPanel>
    </Border>
    <ControlTemplate.Triggers>
        <Trigger Property="IsHighlighted" Value="true">
            <Setter TargetName="Border" Property="Background" Value="{StaticResource SelectedBackgroundBrush}"/>
        </Trigger>
        <Trigger Property="IsEnabled" Value="false">
            <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

<ComboBox Name="c_comboBox" ItemsSource="{Binding}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Path=ShortDescription}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
    <ComboBox.ItemContainerStyle>
        <Style TargetType="{x:Type ComboBoxItem}">
            <Setter Property="Template" Value="{StaticResource FullDescriptionTemplate}" />
        </Style>
    </ComboBox.ItemContainerStyle>
</ComboBox>

这会导致以下行为：