分配新的处理程序时如何引发事件？

Question

我正在尝试复制现有.NET XNA类事件提供的功能： NetworkSession.GamerJoined 。

将事件分配给事件后，可以立即引发该事件，例如：

myNetworkSession.GamerJoined += GamerJoinedEventHandler;

void GamerJoinedEventHandler(object sender, GamerJoinedEventArgs e)
{
    // If you put a beakpoint on the assignment line above and another here
    // this handler is called during the assignment.
}

如果我使用GamerJoined事件编写自己的NetworkSession类，该如何实现？

Answer 1

是的，您可以使用add contextual关键字执行此操作。

当您有一行时：

public event EventHandler<GamerJoinedEventArgs> GamerJoined;

这是用于以下方面的语法糖：

public event EventHandler<GamerJoinedEventArgs> GamerJoined
{
    add
    {
        this.gamerJoined += (EventHandler<GamerJoinedEventArgs>)Delegate.Combine(this.gamerJoined, value);
    }
    remove
    {
        this.gamerJoined -= (EventHandler<GamerJoinedEventArgs>)Delegate.Remove(this.gamerJoined, value);
    }
}

其中gamerJoined是该事件的私人支持字段。 因此，您可以编写自己的add来调用处理程序，例如

public event EventHandler<GamerJoinedEventArgs> GamerJoined
{
    add
    {
        this.gamerJoined += (EventHandler<GamerJoinedEventArgs>)Delegate.Combine(this.gamerJoined, value);
        value(this, new GamerJoinedEventArgs(myGamer));
    }
    remove
    {
        this.gamerJoined -= (EventHandler<GamerJoinedEventArgs>)Delegate.Remove(this.gamerJoined, value);
    }
}