WPF 资源样式第一次不显示

Question

当我将集合绑定(bind)到以下窗口和用户控件时，样式不起作用。

当我按下窗口上的按钮时，样式就会启动。

是什么阻止我的样式在初始绑定(bind)时触发？

<Grid>
    <ItemsControl Name="LbItems" ItemsSource="{Binding MyData}">
        <ItemsControl.Resources>
            <DataTemplate DataType="{x:Type viewModel:SomeViewModel}">
                <control:SomeView Margin="5" />
            </DataTemplate>
            <DataTemplate DataType="{x:Type viewModel:AnotherViewModel}">
                <control:AnotherView Margin="5" />
            </DataTemplate>
        </ItemsControl.Resources>
    </ItemsControl>
</Grid>

我有一个用户控件，如下所示:

<UserControl.Resources>
    <Style TargetType="{x:Type TextBlock}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding RelativeSource={x:Static 
                RelativeSource.Self}, Path=DataContext.Selected}" Value="False">
                <Setter Property="Foreground">
                    <Setter.Value>
                        Red
                    </Setter.Value>
                </Setter>
            </DataTrigger>
            <DataTrigger Binding="{Binding RelativeSource={x:Static 
                RelativeSource.Self}, Path=DataContext.Selected}" Value="True">
                <Setter Property="Foreground">
                    <Setter.Value>
                        DarkSeaGreen
                    </Setter.Value>
                </Setter>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</UserControl.Resources>

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="Auto"/>
    </Grid.ColumnDefinitions>
    <Button Command="{Binding SelectCommand}"  Content="+" HorizontalAlignment=
        "Left" VerticalAlignment="Top" Width="25" Grid.Column="0"/>
    <TextBlock HorizontalAlignment="Left" Margin="5" TextWrapping="Wrap" Text=
        "{Binding Endorsement.Name}" VerticalAlignment="Top" Grid.Column="1" />
    <Button Command="{Binding DeselectCommand}" Content="-" HorizontalAlignment=
        "Right" VerticalAlignment="Top" Width="25" Grid.Column="2"/>
</Grid>

Answer 1

页面加载时和设置“Selected”时是两个不同的时间；因此，当页面加载并且没有任何反应时，selected 为空。预测空情况，例如添加样式

<DataTrigger Binding="{Binding RelativeSource={x:Static 
                RelativeSource.Self}, Path=DataContext.Selected}" Value="{x:Null}">
  ...