如何将属性附加到自定义事件？

Question

我有一个自定义事件，并想为其附加一个属性（一个字符串就可以了）。 我需要在我的代码中更改什么：

    public static readonly RoutedEvent ModelClickEvent = EventManager.RegisterRoutedEvent(
        "ModelClick", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(InfoBox));

    // Provide CLR accessors for the event
    public event RoutedEventHandler FadeIn
    {
        add { AddHandler(ModelClickEvent, value); }
        remove { RemoveHandler(ModelClickEvent, value); }
    }

    // This method raises the Tap event
    void RaiseTapEvent()
    {
        RoutedEventArgs newEventArgs = new RoutedEventArgs(InfoBox.FadeInEvent); 
        RaiseEvent(newEventArgs);
    }

Answer 1

首先，您需要创建一个新的 RoutedEventArgs 派生类，其中包含您的新属性。比如：

public class ModelClickEventArgs : RoutedEventArgs
{
    public string MyString { get; set; }
    public ModelClickEventArgs() : base() { }
    public ModelClickEventArgs(RoutedEvent routedEvent) : base(routedEvent) { }
    public ModelClickEventArgs(RoutedEvent routedEvent, object source) : base(routedEvent, source) { }
}

然后，您必须创建一个使用新事件参数的委托：

public delegate void ModelClickEventHandler(object sender, ModelClickEventArgs e);

之后，您必须对上面的代码进行更改，以便它使用这些新对象：

public static readonly RoutedEvent ModelClickEvent = EventManager.RegisterRoutedEvent(
        "ModelClick", RoutingStrategy.Bubble, typeof(ModelClickEventHandler), typeof(Window));

// Provide CLR accessors for the event
public event ModelClickEventHandler FadeIn
{
    add { AddHandler(ModelClickEvent, value); }
    remove { RemoveHandler(ModelClickEvent, value); }
}

// This method raises the Tap event
void RaiseTapEvent()
{
    ModelClickEventArgs newEventArgs = new ModelClickEventArgs();
    newEventArgs.MyString = "some string";
    RaiseEvent(newEventArgs);
}

Answer 2

如果您的意思是要向处理程序接收的 RoutedEventArgs 对象添加一个属性，那么您所要做的就是声明一个继承自 RoutedEventArgs 并具有属性（-y/-ies ) 你想添加。

它看起来像下面这样：

public class ModelRoutedEventArgs : RoutedEventArgs
{
  public string ExtraMessage { get; set; }
  public ModelRoutedEventArgs(RoutedEvent routedEvent, string message) : base(routedEvent)
  {
    ExtraMessage = message;
  }
  // anything else you'd like to add can go here
}

或者，您可以实例化您的自定义 RoutedEventArgs 类并在将其传递给 RaiseEvent() 调用之前设置属性，而不是添加构造函数重载。