纯XAML实现通过按钮关闭ComboBox下拉列表

没问题，我来帮你把这个功能补全！你已经在ComboBox模板里加了按钮，接下来只需要在按钮的Click事件触发器里，用ObjectAnimationUsingKeyFrames直接把ComboBox的IsDropDownOpen属性设为false就行，完全不需要后台代码。

先把你截断的代码补完整，关键的触发器部分应该是这样的：

<Button Grid.Row="1" Width="200" Margin="5" Content="Close ComboBox DropDown">
    <Button.Triggers>
        <EventTrigger RoutedEvent="Button.Click">
            <BeginStoryboard>
                <Storyboard>
                    <ObjectAnimationUsingKeyFrames 
                        Duration="0" 
                        Storyboard.TargetProperty="IsDropDownOpen"
                        Storyboard.Target="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}}">
                        <DiscreteObjectKeyFrame KeyTime="0" Value="False"/>
                    </ObjectAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Button.Triggers>
</Button>

关键说明： #

• Storyboard.Target用RelativeSource={RelativeSource Mode=TemplatedParent}来绑定到模板所属的ComboBox控件，这样就能直接修改它的IsDropDownOpen属性。
• DiscreteObjectKeyFrame的KeyTime="0"和Duration="0"保证点击按钮后下拉框瞬间关闭，没有动画延迟。

如果需要完整的ComboBox模板参考，这里给你一个包含这个按钮的完整示例（基于默认模板修改）：

<Window.Resources>
    <Style x:Key="CustomComboBoxStyle" TargetType="{x:Type ComboBox}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ComboBox}">
                    <Grid>
                        <ToggleButton 
                            x:Name="ToggleButton" 
                            Grid.Column="2" 
                            IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
                            ClickMode="Press"
                            Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}">
                            <Path x:Name="Arrow" Fill="Black" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M 0 0 L 4 4 L 8 0 Z"/>
                        </ToggleButton>
                        <ContentPresenter 
                            x:Name="ContentSite"
                            IsHitTestVisible="False" 
                            Content="{TemplateBinding SelectionBoxItem}"
                            ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
                            ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
                            Margin="3,3,23,3"
                            VerticalAlignment="Center"
                            HorizontalAlignment="Left"/>
                        <TextBox x:Name="PART_EditableTextBox"
                                Style="{x:Null}"
                                Template="{StaticResource ComboBoxTextBox}"
                                HorizontalAlignment="Left"
                                VerticalAlignment="Center"
                                Margin="3,3,23,3"
                                Focusable="True"
                                Background="Transparent"
                                Visibility="Hidden"
                                IsReadOnly="{TemplateBinding IsReadOnly}"/>
                        <Popup 
                            x:Name="Popup"
                            Placement="Bottom"
                            IsOpen="{TemplateBinding IsDropDownOpen}"
                            AllowsTransparency="True" 
                            Focusable="False"
                            PopupAnimation="Slide">
                            <Grid 
                                x:Name="DropDown"
                                SnapsToDevicePixels="True"                
                                MinWidth="{TemplateBinding ActualWidth}"
                                MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                <Border 
                                    x:Name="DropDownBorder"
                                    Background="White"
                                    BorderThickness="1"
                                    BorderBrush="#888"/>
                                <Grid>
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="*"/>
                                        <RowDefinition Height="Auto"/>
                                    </Grid.RowDefinitions>
                                    <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                        <ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained"/>
                                    </ScrollViewer>
                                    <!-- 你添加的关闭按钮 -->
                                    <Button Grid.Row="1" Width="200" Margin="5" Content="Close ComboBox DropDown">
                                        <Button.Triggers>
                                            <EventTrigger RoutedEvent="Button.Click">
                                                <BeginStoryboard>
                                                    <Storyboard>
                                                        <ObjectAnimationUsingKeyFrames 
                                                            Duration="0" 
                                                            Storyboard.TargetProperty="IsDropDownOpen"
                                                            Storyboard.Target="{Binding RelativeSource={RelativeSource Mode=TemplatedParent, AncestorType={x:Type ComboBox}}}">
                                                            <DiscreteObjectKeyFrame KeyTime="0" Value="False"/>
                                                        </ObjectAnimationUsingKeyFrames>
                                                    </Storyboard>
                                                </BeginStoryboard>
                                            </EventTrigger>
                                        </Button.Triggers>
                                    </Button>
                                </Grid>
                            </Grid>
                        </Popup>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="HasItems" Value="False">
                            <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="False">
                            <Setter Property="Foreground" Value="#888"/>
                        </Trigger>
                        <Trigger Property="IsGrouping" Value="True">
                            <Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
                        </Trigger>
                        <Trigger SourceName="Popup" Property="AllowsTransparency" Value="True">
                            <Setter TargetName="DropDownBorder" Property="CornerRadius" Value="4"/>
                            <Setter TargetName="DropDownBorder" Property="Margin" Value="0,2,0,0"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<!-- 使用这个样式的ComboBox -->
<ComboBox Style="{StaticResource CustomComboBoxStyle}" Width="200" Margin="20">
    <ComboBoxItem>Item 1</ComboBoxItem>
    <ComboBoxItem>Item 2</ComboBoxItem>
    <ComboBoxItem>Item 3</ComboBoxItem>
</ComboBox>

这样点击下拉框里的“Close ComboBox DropDown”按钮，就能直接关闭下拉列表了，完全用XAML实现，不需要任何C#代码。

内容的提问来源于stack exchange，提问作者Edgar