触发器（WPF）中的只读附加属性

Question

我遇到只读附加属性的问题。 我用这种方式定义了它：

public class AttachedPropertyHelper : DependencyObject
{

    public static readonly DependencyPropertyKey SomethingPropertyKey = DependencyProperty.RegisterAttachedReadOnly("Something", typeof(int), typeof(AttachedPropertyHelper), new PropertyMetadata(0));

    public static readonly DependencyProperty SomethingProperty = SomethingPropertyKey.DependencyProperty;

}

我想在XAML中使用它：

<Trigger Property="m:AttachedPropertyHelper.Something" Value="0">
                        <Setter Property="FontSize" Value="20"/>
                    </Trigger>

但编译器不想使用它。 结果，我有2个错误：

  

在'ReadonlyAttachedProperty.AttachedPropertyHelper'类型上找不到样式属性'Something'。第11行第16位。

     

在'TextBlock'类型中找不到属性'Something'。

Answer 1

我不知道您的只读附加属性是否有特殊内容，但如果您以默认方式声明它，则可以正常工作：

public class AttachedPropertyHelper : DependencyObject
{
    public static int GetSomething(DependencyObject obj)
    {
        return (int)obj.GetValue(SomethingProperty);
    }

    public static void SetSomething(DependencyObject obj, int value)
    {
        obj.SetValue(SomethingProperty, value);
    }

    // Using a DependencyProperty as the backing store for Something. This enables animation, styling, binding, etc...
    public static readonly DependencyProperty SomethingProperty =
        DependencyProperty.RegisterAttached("Something", typeof(int), typeof(AttachedPropertyHelper), new UIPropertyMetadata(0));
}

修改

如果您想要与只读附加属性相同，请将其更改为：

public class AttachedPropertyHelper : DependencyObject
{
    public static int GetSomething(DependencyObject obj)
    {
        return (int)obj.GetValue(SomethingProperty);
    }

    internal static void SetSomething(DependencyObject obj, int value)
    {
       obj.SetValue(SomethingPropertyKey, value);
    }

    private static readonly DependencyPropertyKey SomethingPropertyKey =
        DependencyProperty.RegisterAttachedReadOnly("Something", typeof(int), typeof(AttachedPropertyHelper), new UIPropertyMetadata(0));

    public static readonly DependencyProperty SomethingProperty = SomethingPropertyKey.DependencyProperty;
}