IObservable -替换AutoResetEvent

Question

只是想知道如何才能替换下面的AutoResetEvent？我试着思考如何用RX的方式或任务来做这件事，但我知道怎么做。

public void LogOnResponse LogOn()
{

    LogOnResponse logOnResponse = null;
    var waitEvent = new AutoResetEvent(false);

    var listener = _connection.LoginStatusEvent
                        .Where(x => x.LoginState == LoginState.LoggedOn 
                                    || x.LoginState == LoginState.LoggedRejected);

    listener.Subscribe(x => {
                            logOnResponse = new LogOnResponse();
                            logOnResponse.InformationMessage = x.Message;
                            logOnResponse.IsAuthenticated = x.LoginState == LoginState.LoggedOn;
                            waitEvent.Set();
                        });

    connection.Login(connectionInfo);

    waitEvent.WaitOne(2000);

    return logOnResponse;
}

Answer 1

考虑像这样构造代码：

var listener = _velocityConnection.LoginStatusEvent
    .Where(x => x.LoginState == LoginState.LoggedOn || x.LoginState == LoginState.LoggedRejected);

var logOnResponse = listener.Select(x =>
    new LogOnResponse() {
        logOnResponse.InformationMessage = x.Message;
        logOnResponse.IsAuthenticated = x.LoginState == LoginState.LoggedOn;
    }
).Timeout(TimeSpan.FromSeconds(2), Observable.Return(new LogOnResponse() {...}))
    .Publish()
    .RefCount();

connection.Login(connectionInfo);
return logOnResponse.First();

我们使用Publish来使执行顺序无关紧要，并使用RefCount()来隐藏ConnectableObservable

Answer 2

我会让这个方法返回一个IObservable<LogOnResponse>，这样你就不需要等到准备好返回的时候了。您还必须注意竞争条件，因为您的登录呼叫可能会在您有机会订阅之前完成。这样的代码应该可以处理竞争条件，并通过返回的IObservable返回响应。很明显，你可以订阅它，一旦LogOnResponse出现，你就可以得到它。

public IObservable<LogOnResponse> LogOn()
{
    return Observable.CreateWithDisposable<LogOnResponse>(observer =>
    {
       var loginDisposable = _velocityConnection.LoginStatusEvent
                        .Where(x => x.LoginState == LoginState.LoggedOn 
                                    || x.LoginState == LoginState.LoggedRejected)
                        .Select(x => {
                            logOnResponse = new LogOnResponse();
                            logOnResponse.InformationMessage = x.Message;
                            logOnResponse.IsAuthenticated = x.LoginState == LoginState.LoggedOn;
                            return logOnResponse;
                        }).Take(1).Subscribe(observer);

       connection.Login(connectionInfo);

       return loginDisposable;
   });
}

这里要注意的一件事是，调用此方法仅返回IObservable。只有在您订阅之后，才会调用实际的登录。

// Gets the IObservable<LogOnResult>
var logonResponseAsObservable = LogOn(); 
//Execute the logon and wait for a response asynchronously
logonResponseAsObservable.Subscribe(response => HandleLogOnResponse(response));