绑定到DataContext的WPF样式DataTrigger不起作用 [英] WPF Style DataTrigger with binding to DataContext not working

问题描述

我有一个文本框，其样式具有更改文本的DataTrigger，如下所示:

I have a TextBox with a style that has a DataTrigger which changes the text, like this:

<Grid>
    <TextBlock Text="Foo">
        <TextBlock.Style>
            <Style BasedOn="{StaticResource TextStyle}" TargetType="TextBlock">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding MyBool}" Value="True">
                        <Setter Property="Text" Value="Bar"/>
                    </DataTrigger>
                 </Style.Triggers>
             </Style>
         </TextBlock.Style>
     </TextBlock>
</Grid>

但是它不起作用，文本永远不会更改为"Bar".我已经测试过将另一个TextBlock与Text ="{Binding MyBool}"一起使用，并且此文本从"False"更改为"True". Snoop没有发现我可以看到的错误，并且输出中没有任何内容.

But it's not working, the text never changes to "Bar". I have tested using another TextBlock with Text="{Binding MyBool}" and this text changes from "False" to "True". Snoop reveals no errors that I can see and there is nothing in the output.

这个问题似乎与 WPF触发器绑定到MVVM属性 >，但我的代码似乎与此处接受的答案没有什么不同( http://www.thejoyofcode.com/以任何相关方式查看Help_Why_cant_I_use_DataTriggers_with_controls_in_WPF.aspx ，使用样式"部分.并按照实际答案中的建议使用DataTemplate似乎是错误的，因为我只希望将其应用于单个TextBlock，但是如果正确，我不确定如何为此编写DataTemplate ...

This question may seem like a duplicate of WPF Trigger binding to MVVM property, but my code does not seem different from the accepted answer there (http://www.thejoyofcode.com/Help_Why_cant_I_use_DataTriggers_with_controls_in_WPF.aspx, section "Using a style") in any relevant way. And using a DataTemplate as suggested in the actual answer seems wrong since I only want this to apply to a single TextBlock, but if it is correct, I'm not sure how to write a DataTemplate for this...

这就是我要绑定的属性的样子:

This is what the property I'm binding to looks like:

public bool MyBool
{
    get { return _myBool; }
    set
    {
        if (_myBool== value)
            return;

        _myBool= value;
        NotifyPropertyChanged();
    }
}
private bool _myBool;

推荐答案

依赖项属性可以在许多不同的地方进行设置；内联，动画，强制，触发器等.例如

Dependency Properties can be set from many different places; inline, animations, coercion, triggers, etc. As such a Dependency Property Value Precedence list was created and this dictates which changes override which other changes. Because of this order of precedence, we can't use a Trigger to update a property that is explicitly set inline in your XAML. Try this instead:

<Grid>
    <TextBlock>
        <TextBlock.Style>
            <Style BasedOn="{StaticResource TextStyle}" TargetType="TextBlock">
                <!-- define your default value here -->
                <Setter Property="Text" Value="Foo" />
                <Style.Triggers>
                    <DataTrigger Binding="{Binding MyBool}" Value="True">
                        <!-- define your triggered value here -->
                        <Setter Property="Text" Value="Bar" />
                    </DataTrigger>
                 </Style.Triggers>
             </Style>
         </TextBlock.Style>
     </TextBlock>
</Grid>

这篇关于绑定到DataContext的WPF样式DataTrigger不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！