wpf - 附加属性的样式触发器

Question

我创建了自己的附加属性，如下所示:

 public static class LabelExtension
    {
        public static bool GetSelectable(DependencyObject obj)
        {
            return (bool)obj.GetValue(SelectableProperty);
        }
        public static void SetSelectable(DependencyObject obj, bool value)
        {
            obj.SetValue(SelectableProperty, value);
        }
        // Using a DependencyProperty as the backing store for Selectable.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SelectableProperty =
            DependencyProperty.RegisterAttached("Selectable", typeof(bool), typeof(Label), new UIPropertyMetadata(false));
    }

然后我正在尝试创建一种带有依赖于它的触发器的样式:

<!--Label-->
<Style TargetType="{x:Type Label}">
    <Style.Triggers>
        <Trigger Property="Util:LabelExtension.Selectable" Value="True">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Label}">
                        <TextBox IsReadOnly="True" Text="{TemplateBinding Content}" />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Trigger>
    </Style.Triggers>
</Style>

但是我遇到了运行时异常:

Cannot convert the value in attribute 'Property' to object of type 'System.Windows.DependencyProperty'.  Error at object 'System.Windows.Trigger' in markup file 

如何在样式触发器中访问附加属性的值？我曾尝试将 DataTrigger 与 RelativeSource 绑定(bind)一起使用，但它并没有通过该值。

Answer 1

您的触发器声明很好，但您附加的属性声明有一个小故障。依赖属性的所有者类型必须是声明它的类型，而不是您计划将其附加到的类型。所以这:

DependencyProperty.RegisterAttached("Selectable", typeof(bool), typeof(Label)...

需要改成这样:

DependencyProperty.RegisterAttached("Selectable", typeof(bool), typeof(LabelExtension)...
                                                                ^^^^^^^^^^^^^^^^^^^^^^