通过Style设置隐藏的AttachedProperty

Question

我在使用 System.Windows.Interactivity.Interaction 附加行为类（来自 Expression Blend SDK 4）时遇到问题。我想在 XAML 样式元素中为 System.Windows.Window 类定义一对触发器。但由于 System.Windows.Interactivity.Interaction 类的 TriggersProperty 字段是私有的，并且此类中没有 SetTriggers 方法，因此我已经出现错误'设置属性 System.Windows.Setter.Property 引发异常。 ->值不能为空。运行以下代码时的参数名称：property'。

我真的很想在样式中使用触发器和操作，因为我想将它们用于我的窗口后代控件。当然，我可以使用我的自定义行为或直接使用触发器模拟逻辑对我的窗口后代类进行编码，但我想使用表达式库和我自己的现有触发器和操作，而不是拒绝它们，仅仅是因为 < Interaction类的em>TriggersProperty是隐藏的，我无法通过样式设置它。

有解决该问题的方法吗？通过反射还是其他方式？

附言。我已经尝试声明带有 TriggersProperty 附加依赖属性的自定义静态类，并在 AddOwner 方法的帮助下注册，但没有帮助 - 最后它仍然尝试访问相同的TriggersProperty 在同一个 System.Windows.Interactivity.Interaction 类中。

<Window
    x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:windowsInteractivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity">
    <Window.Style>
        <Style TargetType="Window">
            <Setter Property="Title" Value="WindowStyleTest"/>
            <Setter Property="windowsInteractivity:Interaction.Triggers">
                <Setter.Value>
                    <windowsInteractivity:EventTrigger EventName="MouseDown"/>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Style>
</Window>

Answer 1

！！！更新！！！

好吧，我更进一步了。我扩展了该扩展以执行所有工作，包括设置触发器集合。

触发集合扩展
扩展可以完成所有繁重的工作。
注意：第一次调用 ProvideValue 时会加载样式，因此 TargetValue 是一个 Setter。

[ContentProperty("Triggers")] 
public class TriggerCollectionExtension : MarkupExtension
{
    public string EventName { get; set; }

    public string CommandName { get; set; }

    public object CommandParameter { get; set; }


    public System.Windows.Interactivity.TriggerCollection Triggers { get; private set;}

    public TriggerCollectionExtension()
    {
        var trigCollectionType = 
            typeof(System.Windows.Interactivity.TriggerCollection);

        var triggers = (System.Windows.Interactivity.TriggerCollection)
                        trigCollectionType.GetConstructor( 
                        BindingFlags. NonPublic | BindingFlags. Instance, 
                        null, Type.EmptyTypes, null).Invoke (null);

        // Cheat to get around this problem.
        // must have IsFrozen set to false to modify
        var methCreateCore = trigCollectionType.GetMethod("CreateInstanceCore", 
            BindingFlags.NonPublic | BindingFlags.Instance);
        var cloneTriggers = 
            (System.Windows.Interactivity.TriggerCollection)
             methCreateCore.Invoke(triggers, null);

        this.Triggers = cloneTriggers;
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var target = serviceProvider.GetService(typeof(IProvideValueTarget)) as         
            IProvideValueTarget;

        // The first time this is called is when loading the style.
        // At that point the TargetObject is of type Setter.
        // Return this (The MarkupExtension) and it will be reevaluated when the style 
        // is applied.

        var hostcontrol = target.TargetObject as Control;
        if (hostcontrol != null)
        {
            var cloneTriggers = this.Triggers;

            var eventTrigger = new EventTrigger(this.EventName);

            var trigbase = eventTrigger as TriggerBase;
            trigbase.Attach(hostcontrol);

            var commandAction = new CommandAction(hostcontrol, this.CommandName, 
                this.CommandParameter);
            eventTrigger.Actions.Add(commandAction);

            cloneTriggers.Add(eventTrigger);

            Interaction.SetShadowTriggers(hostcontrol, this.Triggers);

            return null;
        }
        else
        {
            return this;
        }

        return null;
    }
}

互动
TriggersCollection 的重新所有权/公开。

<!-- language: c# -->
/// <summary>
/// Helps workaround the bug in the deployed interaction DLL.
/// The DependencyProperty is registered as ShadowTriggers and the Setter Getter is   
/// SetTriggers() GetTriggers().
/// The result is compile error for XAML if anything but Shadowtriggers is used and 
/// runtime error.
/// </summary>
public static class Interaction
{
    static Interaction()
    {
        var interActionType = typeof(System.Windows.Interactivity.Interaction);
        var triggersProperty = (DependencyProperty)interActionType.InvokeMember(
            "TriggersProperty", 
            BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.GetField, 
            null, null, null);

        ShadowTriggersProperty = triggersProperty.AddOwner(typeof(Interaction));
    }

    public static readonly DependencyProperty ShadowTriggersProperty;

    public static System.Windows.Interactivity.TriggerCollection 
       GetShadowTriggers(DependencyObject d)
    {
        return 
          (System.Windows.Interactivity.TriggerCollection)
          d.GetValue(ShadowTriggersProperty);
    }

    public static void 
       SetShadowTriggers(
         DependencyObject d, 
         System.Windows.Interactivity.TriggerCollection value)
    {
        d.SetValue(ShadowTriggersProperty, value);
    }
}

命令操作
一个自定义 TriggerAction，用于在 DataContext 上查找命令。

<!-- language: c# -->
public class CommandAction : TriggerAction<FrameworkElement>
{
    FrameworkElement control;
    private string commandName;
    object commandParameter;

    private ICommand actualCommand;

    public CommandAction(FrameworkElement control, string commandName, 
            object commandParameter)
    {
        this.control = control;
        this.commandName = commandName;
        this.commandParameter = commandParameter;

        object datacontext;

        if (this.FindDataContext(this.control, out datacontext))
        {
            var datacontextType = datacontext.GetType();
            var propCommand = datacontextType.GetProperty(this.commandName);

            this.actualCommand = propCommand.GetValue(datacontext, null) as ICommand;
        }
    }

    private bool FindDataContext(FrameworkElement control, out object datacontext)
    {
        datacontext = default(object);

        var parent = VisualTreeHelper.GetParent(control);
        while (parent != null)
        {
            var parentFrame = parent as FrameworkElement;
            if (parentFrame != null)
            {
                datacontext = parentFrame.DataContext;
                if (datacontext != null)
                {
                    return true;
                }
            }

            var parentFrameContent = parent as FrameworkContentElement;
            if (parentFrameContent != null)
            {
                datacontext = parentFrameContent.DataContext;
                if (datacontext != null)
                {
                    return true;
                }
            }

            parent = VisualTreeHelper.GetParent(parent);
        }

        return false;
    }

    protected override void Invoke(object parameter)
    {
        if (this.actualCommand != null)
        {
            if (this.actualCommand.CanExecute(parameter))
            {
                this.actualCommand.Execute(parameter);
            }
        }
    }
}

哇，老读者第一次发布代码。我终于明白了为什么代码的剪切和粘贴效果并不总是那么好。经过多次尝试才提交此更新。

我确信有磁盘空间、解析或渲染速度等原因，并且编辑器在提交失败时保持状态良好。

Answer 2

我明白了，为什么会出现这个错误。这是因为在运行时它通过字符串名称搜索附加依赖项属性，即“ShadowTriggers”（如 System.Windows.Interactivity 程序集 Interaction 静态构造函数中指定的那样）。因此，我创建了自己的自定义静态类，并从 System.Windows.Interaction 继承了触发器依赖属性（通过 Reflection 和 AddOwner，只是将该属性公开为 ShadowTriggersProperty）。成功了！但是...现在我必须向样式的属性值设置器提供一个 TriggerCollection 实例，并且该类的构造函数是内部的。假设已经没有路可走了。