C# data-binding windows-phone-7 dependency-properties

WP7：绑定到附加属性

发布于 2024-11-30 14:30:09 字数 949 浏览 1 评论 0原文

我正在尝试将数据值绑定到附加属性。然而，它就是无法让它发挥作用。

我将其定义为：

public static class MyClass
{
    public static readonly DependencyProperty MyPropertyProperty =
        DependencyProperty.RegisterAttached("MyProperty", typeof(string),
        typeof(MyClass), new PropertyMetadata(null));

    public static string GetMyProperty(DependencyObject d)
    {
        return (string)d.GetValue(MyPropertyProperty);
    }

    public static void SetMyProperty(DependencyObject d, string value)
    {
        d.SetValue(MyPropertyProperty, value);
    }
}

现在我使用的 XAML 看起来像这样：

<TextBlock local:MyClass.MyProperty="{Binding MyStringValue}" />

我在 SetMyProperty 方法中设置了一个断点，但它从未被调用。它不会引发任何错误，只是从未设置或要求。但是，如果我将 XAML 中的值更改为固定字符串，则会调用：

<TextBlock local:MyClass.MyProperty="foobar" />

我缺少什么？

注意：上面的示例是显示相同奇怪行为的最小版本。当然，我的实际实现比这更有意义。

预先感谢您的任何提示！

原文

I'm trying to bind a data value to an attached property. However, it just dont get it to work.

I defined it like:

public static class MyClass
{
    public static readonly DependencyProperty MyPropertyProperty =
        DependencyProperty.RegisterAttached("MyProperty", typeof(string),
        typeof(MyClass), new PropertyMetadata(null));

    public static string GetMyProperty(DependencyObject d)
    {
        return (string)d.GetValue(MyPropertyProperty);
    }

    public static void SetMyProperty(DependencyObject d, string value)
    {
        d.SetValue(MyPropertyProperty, value);
    }
}

Now the XAML I use it looks something like this:

<TextBlock local:MyClass.MyProperty="{Binding MyStringValue}" />

I set a breakpoint in the SetMyProperty method, but it is never called. It does not raise any error, it is just never set or asked for. However, if I change the value in XAML to a fixed string, it gets called:

<TextBlock local:MyClass.MyProperty="foobar" />

What am I missing?

Note: the above example is the minimal version that shows the same strange behavior. My actual implementation makes more sense than this of course.

Thanks in advance for any hint!

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撩人痒 2024-12-07 14:30:09

并且绑定永远不会触发您的 SetMyProperty - 如果您需要控制值何时更改，则必须使用 PropertyMetadata 需要一个“Change”-Handler



... new PropertyMetadata(
    null,
    new PropertyChangedCallback((sender, e) => {
      var myThis = (MyClass)sender;
      var changedString = (string)e.NewValue;
      // To whatever you like with myThis ( = the sender object) and changedString (= new value)
    })

And the binding wont trigger your SetMyProperty ever - if you need controll over when the value changes you must use the override of PropertyMetadata that expects a "Change"-Handler



... new PropertyMetadata(
    null,
    new PropertyChangedCallback((sender, e) => {
      var myThis = (MyClass)sender;
      var changedString = (string)e.NewValue;
      // To whatever you like with myThis ( = the sender object) and changedString (= new value)
    })

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