在WPF中绑定Setter属性的值 [英] Binding the value of a Setter Property in WPF

问题描述

我整天都在寻找一种方法来在 ComboBox 上显示默认文本字符串，而我设法找到的最接近的示例就是使用水印的示例.当我的应用程序打开时， ComboBox 的Visibility属性设置为Collapsed，然后通过命令使其可见.不幸的是，我没法跟上水印.这是我正在使用的东西:

I have spent all day looking for a way to display a default string of text on a ComboBox and the closest I managed to find that worked was an example that uses watermarking. When my application opens, the ComboBox's Visibility property is set to Collapsed and then made visible by a command. Unfortunately, I can't get the watermark to follow suit. Here is what I'm working with:

<Style x:Key="watermarkLabelStyle">
    <Setter Property="TextBlock.Foreground" Value="Black" />
    <Setter Property="FrameworkElement.Opacity" Value="0.8" />
    <Setter Property="TextBlock.FontSize" Value="12" />
    <Setter Property="TextBlock.FontStyle" Value="Italic" />
    <Setter Property="TextBlock.Margin" Value="8,4,4,4" />
    <Setter Property="TextBlock.Visibility" Value="{Binding Visible}" />
</Style>

{Binding Visible} 无效，即使窗口中的其他控件已绑定并正常运行.

{Binding Visible} has no effect even though other controls in the window are bound to it and behave properly.

<ComboBox ItemsSource="{Binding LeagueFormatsNode}"
          x:Name="leagueFormatComboBox"
          Grid.Column="0"
          Grid.Row="1"
          Grid.ColumnSpan="3"
          ScrollViewer.CanContentScroll="False"
          HorizontalContentAlignment="Stretch"
          Visibility="{Binding Visible}"
          Behaviors:WatermarkComboBoxBehavior.EnableWatermark="True"
          Behaviors:WatermarkComboBoxBehavior.Label="Select League Format"
          Behaviors:WatermarkComboBoxBehavior.LabelStyle="{StaticResource watermarkLabelStyle}" /> 

以及viewmodel中的 Visible 属性:

And the Visible property in the viewmodel:

public Visibility Visible
{
    get { return _visibile; }
    set
    {
        if (_visibile == value)
            return;
        _visibile = value;
        RaisePropertyChanged(() => Visible);
    }
}

我该怎么做才能使样式中的setter表现出来并注册绑定?

What can I do to make the setter in the style behave and register the binding?

如果您需要其他代码，我会很乐意提供.

If you need additional code, I'll gladly provide it.

更新:Snoop在TextBlock的Visibility属性上显示绑定错误.在DataContext选项卡上，它说对象为空".我一直在寻找解决此问题的方法，但我一直无法弄清楚该怎么做.如果有人愿意把我推向正确的方向，我当然会很感激.代码来自此处 http://archive.msdn.microsoft.com/Release/ProjectReleases.aspx?ProjectName=PierreCode&ReleaseId=3546

Update: Snoop is showing a binding error on the TextBlock's Visibility property. On the DataContext tab, it says "object is null". I have been looking for a way to fix this but I haven't been able to figure out how. If anybody would be kind enough to push me in the right direction, I would certainly appreciate it. The code came from here http://archive.msdn.microsoft.com/Release/ProjectReleases.aspx?ProjectName=PierreCode&ReleaseId=3546

我并不一定要寻求完整的演练，只是足够的指导以指导我解决问题.

I'm not necessarily looking for a complete walkthrough, just enough advice to guide me to the solution.

推荐答案

根据您发布的代码，我假设您使用的是

Based on your posted code I'm assuming your using the Behavior from Here

现在，如果您在上述链接中下载示例zip，则将获得5个文件，这些文件为您提供了这组 Behavior (位于 Behavior 文件夹中).

Now if you download the sample zip in the above Link, you got 5 files that give you this set of Behavior's(found in the Behavior folder).

编辑 TextBlockAdorner.cs

在该行之后的构造函数中

In the constructor just after the line

m_TextBlock = new TextBlock { Style = labelStyle, Text = label };

添加

m_TextBlock.DataContext = adornedElement;

现在在您的 Style 设置器中，将您的 Binding 切换为

Now in your Style setter switch your Binding to

<Setter Property="TextBlock.Visibility"
        Value="{Binding DataContext.Visible}" />

您应该完成了.

注释:

• 请勿在VM中保留 System.Windows.Visibility .将VM中的 Visibility 属性保留为 bool ，并且在xaml中将 Binding 保留时，使用 BooleanToVisibilityConverter (直接提供)在xaml中.您不必创建一个)
• 当您定义 Style 时，习惯于指定 Type ="..." .它不仅可以帮助您一目了然地确定与样式有关的 Style ，而且还可以为您的每个setter属性节省一些多余的类型限定.

• Do not hold System.Windows.Visibility in your VM. Keep Visibility property in the VM as a bool and when your Binding it in xaml use a BooleanToVisibilityConverter(available directly in xaml. You do not have to create one)
• When your defining Style's get into the habit of specifying a Type="...". It not only helps identify at a glance which Style's relate to what but also saves some redundant type qualification for each of your setter properties.

类似

<Setter Property="FrameworkElement.Opacity"
        Value="0.8" />

将是

<Style x:Key="watermarkLabelStyle"
        TargetType="{x:Type TextBlock}">
  ...
  <Setter Property="Opacity"
          Value="0.8" />

• 最后希望这只是您代码中的错字，但如果不是，请尝试遵循一些有关属性的命名约定.在您的VM中，您的媒体资源称为 Visible ，而其私有后端为 _visibile .
• Finally hopefully this is just a typo in your code but if not try to follow some naming convention with your Properties. In your VM, your property is called Visible while it's private back-end is _visibile.

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