c# - 异步任务如何有条件返回

Question

您好，我正在尝试有条件地返回异步方法任务。以下是我尝试过的方法。

public string DoMessage(MyObj obj)
    {
        string returnStatus = "Processing...";
        var storageAccount = CloudStorageAccount.DevelopmentStorageAccount;
        var queueClient = storageAccount.CreateCloudQueueClient();

        var queue = queueClient.GetQueueReference(ConfigurationManager.AppSettings["QueueName"]);
        if (queue.CreateIfNotExists())            {
        }

        var msg = CloudQueueMessageExtensions.Serialize(obj);
        queue.AddMessage(msg);

        //Task processTask = RunMessageProces();
        var t = Task.Run(() => RunMessageProces());
        t.Wait();
        return  returnStatus;
    }

    private async Task<string> RunMessageProces()  
    {
        statusProcess = "Your message successfully inserted in process queue.";
        await Task.Run(() => {
            lock (_oQueue)
            {
                if (flagProcessing == true) //return when queue processing alredy started
                {
                    return statusProcess; //Error ..??? how to return 
                }
                flagProcessing = true; //else start processing the queue till there are messages.
            }
        });
        statusProcess = ProcessMyMessage();
        return statusProcess;
    }

    private string ProcessMyMessage() {...}

我缺少什么？如何在异步方法下有条件地返回字符串，该方法也位于等待锁匿名 block 内(？)。我在任务中执行异步操作，因为由于服务的暴露部分，Do Message 同时被大量调用淹没。

Answer 1

我假设您询问如何访问任务的返回值。

  private async Task<string> RunMessageProces()
    {
        var statusProcess = "Your message successfully inserted in process queue.";
       var retValue =  await Task.Run(() =>
        {
            lock (_oQueue)
            {
                if (flagProcessing == true) //return when queue processing alredy started
                {
                    return "Error"; // or some such error indicator
                }
                flagProcessing = true; //else start processing the queue till there are messages.
            }
            return string.Empty; // return a string here too....
        });

        // if( retValue == "Error" ) { return "Error" } 
        statusProcess = ProcessMyMessage();
        return statusProcess;
    }