在设计时未附加Silverlight混合行为 [英] Silverlight Blend Behaviors do not get attached at design time

问题描述

我已经开发了一种行为，该行为更改了AssociatedObject的Clip属性.当我运行该应用程序时，一切都很好.但是，当我在Blend中查看页面时，该行为似乎并不影响其关联对象.

I have developed a behavior that changes the Clip property of the AssociatedObject. When I run the application, all is well. But when I view the page in Blend it appears like the behavior does not affect its associated object.

我试图通过将Visual Studio 2010调试器附加到它的进程来调试"混合，并在行为的OnAttached方法上设置一个断点，但是从未达到断点.好像blend阻止了该行为在设计时那样.

I tried to "debug" blend by attaching visual studio 2010 debugger to it's process and set a break point on the behavior's OnAttached method, but the breakpoint is never reached. As if blend prevents that behavior from being attached at design time.

有办法解决吗?

干杯

推荐答案

我终于找到了一种可行的解决方法，但是在此答案的结尾我有一个很大的警告.这是我的CustomAttachManager:

I finally found a workable way around it, but there's a big caveat which I put at the end of this answer. Here's my CustomAttachManager:

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如下行为:

You can then use it to attach behaviors like this:

<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，这在设计器中是可见的.

My example behavior changes the background of a panel to red, which is visible in the designer.

剩下的问题是多种行为的情况.我能想到的最好的解决方案是代理:

The remaining problem is the case of multiple behaviors. The best solution I could come up with is a proxy:

[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();
    }
}

可通过以下方式使用:

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

代理具有一个缺陷，即它无法正确处理在已附加某些东西之后添加的行为，但是在经典用例中不会发生这种情况.

The proxy has a defect in that it won't properly handle behaviors added after something already got attached, but that is not going to happen in the classic use case.

需要注意的是，我不知道使Blend显示对象树中行为的方法.无法使用"AlternateContentProperty"，因为它不适用于CustomAttachManager使用的附加属性.

The caveat is that I don't know a way to make Blend display the behaviors in the object tree. The "AlternateContentProperty" can't be used because it doesn't work for attached properties, which is what CustomAttachManager uses.

如果我找到此问题的答案，我将更新此答案.

I will update this answer should I find an answer to this problem.

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