如何删除(3 个状态)选中的列表框项目周围不需要的红色边框?

How to remove unwanted red border around (3 state) checked listbox items?

我创建了一个 ListBox,每个 ListBox 项都有一个三态 CheckBox,每个状态都有一个自定义 CheckBox 图像。问题是,当项目设置为第三种 (null) 状态时,项目周围会出现不需要的红色边框,我不知道为什么会出现这种情况或如何删除它。

列表框的样式如下:

<Style x:Key="ThreeStateCheckBoxListStyle" TargetType="{x:Type ListBox}">
    <Setter Property="SelectionMode" Value="Multiple"></Setter>
    <Setter Property="Margin" Value="8"></Setter>
    <Setter Property="Background" Value="Transparent"></Setter>
    <Setter Property="ItemContainerStyle">
        <Setter.Value>
            <Style TargetType="{x:Type ListBoxItem}">
                <Setter Property="Margin" Value="2" />
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type ListBoxItem}">
                            <CheckBox Focusable="False" Foreground="{StaticResource textBrush}" 
                                      IsThreeState="True" IsChecked="{Binding Path=IsSelected, Mode=TwoWay,
                                        RelativeSource={RelativeSource TemplatedParent}}">
                                <CheckBox.Template>
                                    <ControlTemplate TargetType="{x:Type CheckBox}">
                                        <StackPanel Orientation="Horizontal">
                                            <Image x:Name="checkboxImage" Source="pack://application:,,,/Images/CheckBoxUncheck_16x.png" Width="16"
                                                   Margin="0,0,2,0" />
                                            <ContentPresenter/>
                                        </StackPanel>
                                        <ControlTemplate.Triggers>
                                            <Trigger Property="IsChecked" Value="True">
                                                <Setter TargetName="checkboxImage" Property="Source" Value="pack://application:,,,/Images/CheckBox_16x.png"/>
                                            </Trigger>
                                            <Trigger Property="IsChecked" Value="{x:Null}">
                                                <Setter TargetName="checkboxImage" Property="Source" Value="pack://application:,,,/Images/CheckBoxExclude_16x.png"/>
                                            </Trigger>
                                        </ControlTemplate.Triggers>
                                    </ControlTemplate>
                                </CheckBox.Template>
                                <ContentPresenter></ContentPresenter>
                            </CheckBox>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </Setter.Value>
    </Setter>
</Style>

在我看来像这样的绑定

IsChecked="{Binding Path=IsSelected, 
                    Mode=TwoWay,
                    RelativeSource={RelativeSource TemplatedParent}}"

负责观测结果,因为CheckBox.IsChecked可以是True | False | null (Nullable<bool>), 当 ListBoxItem.IsSelectedbool

如果我设置详细的跟踪信息,使用 PresentationTraceSources.TraceLevel=High

IsChecked="{Binding Path=IsSelected, 
                    Mode=TwoWay,
                    PresentationTraceSources.TraceLevel=High,
                    RelativeSource={RelativeSource TemplatedParent}}"

我得到:

BindingExpression : GetValue at level 0 from ListBoxItem using DependencyProperty(IsSelected): 'False'
BindingExpression : TransferValue - got raw value 'False'
BindingExpression : TransferValue - using final value 'False'
BindingExpression : Update - got raw value 'True'
BindingExpression : Update - using final value 'True'
BindingExpression : SetValue at level 0 to ListBoxItem using DependencyProperty(IsSelected): 'True'
BindingExpression : GetValue at level 0 from ListBoxItem using DependencyProperty(IsSelected): 'True'
BindingExpression : TransferValue - got raw value 'True'
BindingExpression : TransferValue - using final value 'True'
BindingExpression : Update - got raw value <null>
BindingExpression : Update - using final value {DependencyProperty.UnsetValue}

null 导致 {DependencyProperty.UnsetValue} 并且它是 bool IsSelected 属性

的错误

项目周围的红色边框是默认设置 Validation.ErrorTemplate。您可以在 CheckBox

上禁用它
<CheckBox Validation.ErrorTemplate="{x:Null}" Focusable="False" ...

请注意,处于不确定状态 (IsChecked=null) 的 CheckBox 不会清除对 ListBoxItem 的选择