Silverlight混合行为在设计时不会附加

public class CustomAttachManager : DependencyObject
{
    #region Object CustomAttachManager.Attached = null

    public static IAttachedObject GetAttached(DependencyObject obj) { return (IAttachedObject)obj.GetValue(AttachedProperty); }
    public static void SetAttached(DependencyObject obj,IAttachedObject value) { obj.SETVALue(AttachedProperty,value); }

    public static readonly DependencyProperty AttachedProperty =
        DependencyProperty.RegisterAttached("Attached",typeof(IAttachedObject),typeof(CustomAttachManager),new PropertyMetadata(null,StaticHandleAttachedChanged));

    static void StaticHandleAttachedChanged(DependencyObject self,DependencyPropertyChangedEventArgs args)
    {
        var ov = (IAttachedObject)args.OldValue;
        var nv = (IAttachedObject)args.NewValue;

        if (ov != null) ov.Detach();
        if (nv != null) nv.Attach(self);
    }
    #endregion
}

然后,您可以使用它来附加这样的行为：

<my:CustomAttachManager.Attached>
    <my:redBACkgroundBehavior></my:redBACkgroundBehavior>
</my:CustomAttachManager.Attached>

我的示例行为将面板的背景更改为红色,这在设计器中可见.

剩下的问题是多种行为的情况.我能提出的最佳解决方案是代理：

[ContentProperty("Children")]
public class MultipleBehavior : Behavior<DependencyObject>
{
    DependencyObjectCollection<IAttachedObject> children = new DependencyObjectCollection<IAttachedObject>();
    public DependencyObjectCollection<IAttachedObject> Children { get { return children; } }

    protected override void OnAttached()
    {
        foreach (var child in Children) child.Attach(AssociatedObject);
    }

    protected override void OnDetaching()
    {
        foreach (var child in Children) child.Detach();
    }
}

可以这样使用：

<my:CustomAttachManager.Attached>
        <my:MultipleBehavior>
            <my:redBACkgroundBehavior />
            <my:SupriseBehavior />
        </my:MultipleBehavior>
    </my:CustomAttachManager.Attached>

代理有一个缺陷,即它不能正确处理已经附加的东西后添加的行为,但在经典用例中不会发生这种情况.

需要注意的是,我不知道如何让Blend在对象树中显示行为.无法使用“AlternateContentProperty”,因为它不适用于附加属性,这是CustomAttachManager使用的属性.

如果我找到这个问题的答案,我会更新这个答案.