WPF基于组合选择的UI元素的可见性

Question

仅在选择组合中的某个项目时尝试显示标签.代码应该解释它.

    <ComboBox Name="comboMyCombo">
        <ComboBoxItem>Don't show the label</ComboBoxItem>
        <ComboBoxItem>Show the label</ComboBoxItem>
    </ComboBox>

    <Label Visibility="Collapsed">This is my label
        <Label.Style>
            <Style>
                <Style.Triggers>
                    <DataTrigger 
                            Binding="{Binding ElementName=comboMyCombo, Path=SelectedValue}" Value="Show the label">
                        <Setter Property="Label.Visibility" Value="Visible"></Setter>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Label.Style>
    </Label>

Answer 1

这里有两个问题.首先,应在样式中指定默认可见性.但即便如此,它也无法工作,因为触发器上的绑定是将SelectedValue,ComboBoxItem对象与字符串对象进行比较,而且永远不会等效.为了简化示例,我在ComboBoxItem的Tag属性中放置了适当的值.虽然比较的实际实施可能会根据应用程序的特定需求而有所不同.

    <ComboBox Name="comboMyCombo">
        <ComboBoxItem Tag="Hide">Don't show the label</ComboBoxItem>
        <ComboBoxItem Tag="Show">Show the label</ComboBoxItem>
    </ComboBox>

    <Label>This is my label
        <Label.Style>
            <Style>
                <Setter Property="Label.Visibility" Value="Collapsed"></Setter>
                <Style.Triggers>
                    <DataTrigger  
                        Binding="{Binding ElementName=comboMyCombo, Path=SelectedItem.Tag}" Value="Show">
                        <Setter Property="Label.Visibility" Value="Visible"></Setter>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Label.Style>
    </Label>

Answer 2

一个"更清洁"的解决方案

<ComboBox>
    <ComboBoxItem x:Name="iOne" Content="One"/>
    <ComboBoxItem x:Name="iTwo" Content="Two"/>
    <ComboBoxItem x:Name="iThree" Content="Three"/>
</ComboBox>

<Label Content="One is shown">
 <Label.Style>
    <Style TargetType="Label">
        <Setter Property="Visibility" Value="Hidden" />
        <Style.Triggers>
            <DataTrigger Binding="{Binding ElementName=iOne, Path=IsSelected}"    Value="True">
                <Setter Property="Visibility"  Value="Visible"/>
            </DataTrigger> 
        </Style.Triggers>
    </Style>
 </Label.Style>
</Label>