C# 基于另一控件的验证设置标签样式

当组合框出现错误时，我希望让组合框旁边的标签文本变为红色，但我当前设置标签文本颜色的方式只会在控件的初始加载时更新。当组合框中的选择发生更改时，如何进行标签验证？或者是否有其他方法更新标签的样式

我有以下XAML：

<Style x:Key="labelStyle" TargetType="Label">
    <Setter Property="HorizontalContentAlignment" Value="Left" />
    <Setter Property="VerticalContentAlignment" Value="Center" />
    <Setter Property="Validation.ErrorTemplate">
        <Setter.Value>
            <ControlTemplate>
                <AdornedElementPlaceholder>
                    <Border BorderBrush="Transparent" BorderThickness="0" />
                </AdornedElementPlaceholder>
            </ControlTemplate>
        </Setter.Value>
    </Setter>

    <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="true">
            <Setter Property="Background" Value="White"/>
            <Setter Property="Foreground" Value="Red"/>
        </Trigger>
    </Style.Triggers>
</Style>

<Label Style="{StaticResource labelStyle}" Content="{Binding Path=Label, ValidatesOnDataErrors=True}" />

<ComboBox ItemsSource="{Binding Path=ItemList}" SelectedItem="{Binding Path=SelectedItem, ValidatesOnDataErrors=True}"/>

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根据您的操作方式，您还需要在“SelectedItem”属性更改时在“Label”属性上引发属性更改

使用仅xaml的解决方案，无需在模型/视图模型（或任何绑定的对象）上具有额外的属性即可完成此操作。如果您有一个组合框，如：

<ComboBox Name="comb" ItemsSource="{Binding Strings}" SelectedValue="{Binding Stringy,ValidatesOnDataErrors=True}" />

你可以像这样使用它：

<Label Content="Select a string" example:LabelValidationHelper.DetailControl="{Binding ElementName=comb}" />

---

您只能使用样式

<Style TargetType="Label">
        <Setter Property="FontSize" Value="20"/>
        <Setter Property="FontWeight" Value="Bold"/>
        <Setter Property="Padding" Value="0,5"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=(Target).(Validation.HasError)}" Value="True">
                <Setter Property="Foreground" Value="Red" />
            </DataTrigger>
            <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=(Target).(Validation.HasError)}" Value="False">
                <Setter Property="Foreground" Value="Gray" />
            </DataTrigger>
        </Style.Triggers>
    </Style>

然后像这样使用它：

<Label Target="{Binding ElementName=NominaalBox}" Content="Nominaal (gram):"/>
<TextBox x:Name="NominaalBox" Text="{Binding Path=NominaalGram, Mode=TwoWay, TargetNullValue='', UpdateSourceTrigger=PropertyChanged}"/>

<Label Content="Select a string" example:LabelValidationHelper.DetailControl="{Binding ElementName=comb}" />

<Style TargetType="Label">
        <Setter Property="FontSize" Value="20"/>
        <Setter Property="FontWeight" Value="Bold"/>
        <Setter Property="Padding" Value="0,5"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=(Target).(Validation.HasError)}" Value="True">
                <Setter Property="Foreground" Value="Red" />
            </DataTrigger>
            <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=(Target).(Validation.HasError)}" Value="False">
                <Setter Property="Foreground" Value="Gray" />
            </DataTrigger>
        </Style.Triggers>
    </Style>

<Label Target="{Binding ElementName=NominaalBox}" Content="Nominaal (gram):"/>
<TextBox x:Name="NominaalBox" Text="{Binding Path=NominaalGram, Mode=TwoWay, TargetNullValue='', UpdateSourceTrigger=PropertyChanged}"/>