如何根据IsValid状态修改ItemsControl内TextBlock与TextBox的前景色？

我定义了如下类：

public class ShippingMethodMap
{
    public string ShippingMethod { get; set; }
    public int? MethodId { get; set; }
    public bool IsManaged { get; set; }
    public bool IsValid { get; set; }
}

数据存储在ObservableCollection<ShippingMethodMap> ShippingMethodMapCollection中，并通过以下XAML代码展示：

<ItemsControl ItemsSource="{Binding Path=ShippingMethodMapCollection}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Border Margin="1" BorderThickness="1" BorderBrush="LightGray">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="50"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0"
                               Text="{Binding Path=ShippingMethod}">
                    </TextBlock>
                    <TextBox Grid.Column="1"
                             Text="{Binding Path=MethodId}"
                             IsEnabled="{Binding Path=IsManaged}">
                    </TextBox>
                </Grid>
            </Border>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

请问当ShippingMethodMap.IsValid为false时，如何将对应项的TextBlock和TextBox的前景色设置为红色？

可以通过WPF的DataTrigger实现这个需求，下面提供几种常用的实现方式：

方式一：通过父元素继承前景色（最简洁） #

利用WPF的属性继承特性，给外层Border添加DataTrigger，当IsValid为false时设置前景色为红色，内部的TextBlock和TextBox会自动继承这个属性：

<ItemsControl ItemsSource="{Binding Path=ShippingMethodMapCollection}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Border Margin="1" BorderThickness="1" BorderBrush="LightGray">
                <Border.Style>
                    <Style TargetType="Border">
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding IsValid}" Value="False">
                                <Setter Property="Foreground" Value="Red"/>
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </Border.Style>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="50"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0"
                               Text="{Binding Path=ShippingMethod}">
                    </TextBlock>
                    <TextBox Grid.Column="1"
                             Text="{Binding Path=MethodId}"
                             IsEnabled="{Binding Path=IsManaged}">
                    </TextBox>
                </Grid>
            </Border>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

方式二：定义共享样式复用逻辑 #

在Grid的资源中定义通用样式，让TextBlock和TextBox共用这个样式，避免重复代码：

<ItemsControl ItemsSource="{Binding Path=ShippingMethodMapCollection}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Border Margin="1" BorderThickness="1" BorderBrush="LightGray">
                <Grid>
                    <Grid.Resources>
                        <Style TargetType="FrameworkElement" x:Key="InvalidForegroundStyle">
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding IsValid}" Value="False">
                                    <Setter Property="Foreground" Value="Red"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </Grid.Resources>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="50"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0"
                               Text="{Binding Path=ShippingMethod}"
                               Style="{StaticResource InvalidForegroundStyle}">
                    </TextBlock>
                    <TextBox Grid.Column="1"
                             Text="{Binding Path=MethodId}"
                             IsEnabled="{Binding Path=IsManaged}"
                             Style="{StaticResource InvalidForegroundStyle}">
                    </TextBox>
                </Grid>
            </Border>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

注：TextBlock和TextBox都继承自FrameworkElement，因此这个通用样式可同时作用于两者。

方式三：单独给每个控件添加触发器 #

如果不需要复用样式，可直接给TextBlock和TextBox分别添加DataTrigger：

<ItemsControl ItemsSource="{Binding Path=ShippingMethodMapCollection}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Border Margin="1" BorderThickness="1" BorderBrush="LightGray">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="50"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0"
                               Text="{Binding Path=ShippingMethod}">
                        <TextBlock.Style>
                            <Style TargetType="TextBlock">
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding IsValid}" Value="False">
                                        <Setter Property="Foreground" Value="Red"/>
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                        </TextBlock.Style>
                    </TextBlock>
                    <TextBox Grid.Column="1"
                             Text="{Binding Path=MethodId}"
                             IsEnabled="{Binding Path=IsManaged}">
                        <TextBox.Style>
                            <Style TargetType="TextBox">
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding IsValid}" Value="False">
                                        <Setter Property="Foreground" Value="Red"/>
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                        </TextBox.Style>
                    </TextBox>
                </Grid>
            </Border>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

内容的提问来源于stack exchange，提问作者Alexey Titov