c# - 如何等待引发 C# 事件？

Question

我有一个 Sender 类，它在 IChannel 上发送一个 Message:

public class MessageEventArgs : EventArgs {
  public Message Message { get; private set; }
  public MessageEventArgs(Message m) { Message = m; }
}

public interface IChannel {
  public event EventHandler<MessageEventArgs> MessageReceived;
  void Send(Message m);
}

public class Sender {
  public const int MaxWaitInMs = 5000;
  private IChannel _c = ...;

  public Message Send(Message m) {
    _c.Send(m);
    // wait for MaxWaitInMs to get an event from _c.MessageReceived
    // return the message or null if no message was received in response
  }
}

当我们发送消息时，IChannel 有时会根据通过引发 MessageReceived 事件发送的 Message 类型做出响应。事件参数包含感兴趣的消息。

我希望 Sender.Send() 方法等待一小段时间以查看是否引发此事件。如果是这样，我将返回其 MessageEventArgs.Message 属性。如果不是，我将返回一个空的 Message。

我怎么能这样等呢？我不希望使用 ManualResetEvents 等进行线程处理，因此坚持使用常规 event 对我来说是最佳选择。

Answer 1

使用 AutoResetEvent。

给我几分钟时间，我会整理一个样本。

这里是:

public class Sender
{
    public static readonly TimeSpan MaxWait = TimeSpan.FromMilliseconds(5000);

    private IChannel _c;
    private AutoResetEvent _messageReceived;

    public Sender()
    {
        // initialize _c
        this._messageReceived = new AutoResetEvent(false);
        this._c.MessageReceived += this.MessageReceived;
    }

    public Message Send(Message m)
    {
        this._c.Send(m);
        // wait for MaxWaitInMs to get an event from _c.MessageReceived
        // return the message or null if no message was received in response


        // This will wait for up to 5000 ms, then throw an exception.
        this._messageReceived.WaitOne(MaxWait);

        return null;
    }

    public void MessageReceived(object sender, MessageEventArgs e)
    {
        //Do whatever you need to do with the message

        this._messageReceived.Set();
    }
}