我试图通过控件模板将Combobox Selected Item属性设置为null我已经添加了Checkbox，因此当Checkbox isChecked为true时，我可以使用datatrigger并将SelectedItem设置为null。基本上我试图添加清除过滤器复选框，当SelectedItem有一些值时会显示，并且点击此复选框后所选项目将自动为空
PS.Initially我打算使用按钮代替复选框，但我不知道如何将它连接到Dictionary里面<CheckBox Panel.ZIndex="2" Width="20" HorizontalAlignment="Left" Foreground="Red" FontWeight="Bold" Background="Red" Content="X" x:Name="chkBOX">
<CheckBox.Style>
<Style TargetType="CheckBox">
<Style.Setters>
<Setter Property="Visibility" Value="Visible"/>
<Setter Property="IsEnabled" Value="True"/>
<Setter Property="VerticalAlignment" Value="Center"/>
</Style.Setters>
<Style.Triggers>
<!-- If selected item is null hide toggle button -->
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}, Path=SelectedItem}" Value="{x:Null}">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
现在我正在寻找与它进行交互，因此当选中复选框时，所选项目将变为空 希望没关系:)）
编辑： 我取得了一些进展 我可以用下面的所选项目为空 但是这仅适用于选定项目未在我的窗体IE上绑定的情况 这工作
<ComboBox Grid.Row="1" Margin="10,0,0,0" ItemsSource="{Binding Users}" Tag="Select Full Name"
DisplayMemberPath="FullName" Template="{DynamicResource ComboBoxWithPlaceholder}" />
这不起作用
<ComboBox Grid.Row="1" Margin="10,0,0,0" ItemsSource="{Binding Users}" Tag="Select Full Name"
DisplayMemberPath="FullName" SelectedItem="{Binding SelectedUserFullName}" Template="{DynamicResource ComboBoxWithPlaceholder}" />
答案 0 :(得分：0)
可安装组合框与安置孔
<ControlTemplate x:Key="ComboBoxWithPlaceholder" x:Name="cb" TargetType="{x:Type ComboBox}">
<Grid x:Name="templateRoot" SnapsToDevicePixels="True">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="16"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition MinWidth="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" Width="0"/>
</Grid.ColumnDefinitions>
<ToggleButton Panel.ZIndex="2" Width="16" HorizontalAlignment="Left" Foreground="Red" ToolTip="Clear Selection" Opacity="0.5"
FontWeight="Bold" Background="Transparent" BorderThickness="0" Content="X" x:Name="toggleB">
<ToggleButton.Style>
<Style TargetType="ToggleButton">
<Style.Setters>
<Setter Property="VerticalAlignment" Value="Center"/>
</Style.Setters>
<Style.Triggers>
<!-- If selected item is null hide toggle button -->
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}, Path=SelectedItem}" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed"/>
<!-- When hidden ensure its not checked -->
<Setter Property="IsChecked" Value="False"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ToggleButton.Style>
</ToggleButton>
<!-- Placeholder textblock text is bound to tag property of combobox -->
<TextBlock Grid.ColumnSpan="2" Grid.Column="0" x:Name="tb" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Foreground="DimGray"
IsHitTestVisible="False" Panel.ZIndex="1" Text="{Binding Tag,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}}">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Setters>
<Setter Property="Visibility" Value="Hidden"/>
<Setter Property="Margin" Value="5,0"/>
<Setter Property="VerticalAlignment" Value="{Binding VerticalContentAlignment,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}}"/>
</Style.Setters>
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}, Path=SelectedItem}" Value="{x:Null}">
<Setter Property="Visibility" Value="Visible"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
<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}" VerticalContentAlignment="Center"
Background="{TemplateBinding Background}" Grid.Column="0" Grid.ColumnSpan="3" 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 Grid.Column="1" x:Name="contentPresenter" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
Content="{TemplateBinding SelectionBoxItem}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
IsHitTestVisible="False" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
</ContentPresenter>
</Grid>
<ControlTemplate.Triggers>
<!-- If selected set selected item to null-->
<DataTrigger Binding="{Binding IsPressed, ElementName=toggleB}" Value="True">
<Setter Property="SelectedValue" Value="{x:Null}"/>
<Setter Property="SelectedValuePath" Value="{x:Null}"/>
<Setter Property="SelectedItem" Value="{x:Null}"/>
</DataTrigger>
<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>
我缺少的是将SelectedValuePath和SelectedValue设置为null以及Selected item
<DataTrigger Binding="{Binding IsPressed, ElementName=toggleB}" Value="True">
<Setter Property="SelectedValue" Value="{x:Null}"/>
<Setter Property="SelectedValuePath" Value="{x:Null}"/>
<Setter Property="SelectedItem" Value="{x:Null}"/>
</DataTrigger>