jQuery Ajax对Web服务的调用似乎是同步的

Question

I have two ajax calls to a web service from jquery.

The first call ( GetMessages ) starts an interval in javascript ( setInterval ) and returns a string array of messages stored in a session variable.

The second call ( UploadUsers ) uploads users and saves the status in the session to be returned in the method GetMessages . So UploadUsers adds messages to the Session and GetMessages retrieves the messages and displays them for the client.

The problem is even though I call both methods asynchronously, GetMessages waits until UploadUsers is finished. It just loads.

I even put a thread.sleep between each user being added and I expect to have GetMessages return "1/10 users have been added", "2/10 users have been added", each on separate calls.

What happens is GetMessages doesn't return anything until UploadUsers is finished and then brings all the text at once.

I have a lot of code so I don't know what to put but here it goes:

UploadUsers.aspx

callAsynchMethod('ClientStatusHandler.asmx/GetMessages',
'', printMessages, stopPollingError);

callAsynchMethod('ClientStatusHandler.asmx/StartRetrievingLeads',
data, stopPolling, stopPollingError);

Site.js

function callAsynchMethod(url, keyValue, callBack, callBackError) {
    $.ajax({
        type: "POST",
        url: url,
        data: keyValue,
        contentType: "application/json; charset=utf-8",
        success: callBack,
        error:callBackError
    });
}

ClientStatusHandler.asmx.cs

const string key = "LUMessages";
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        [WebMethod(EnableSession = true)]
        public string[] GetMessages()
        {

            if (Session[key] != null)
            {
                string[] messages = ((IList<string>)Session[key]).ToArray();
                ((IList<string>)Session[key]).Clear();
                return messages;
            }
            return new string[] { };
        }







  [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
     [WebMethod(EnableSession = true)]
      public string[] UploadUsers()
     {
    //This function adds a user and calls SaveMessageToQueue 
//for every user.
    //I see the message being entered into the session and 
//I call Thread.Sleep(10000) 
    //between messages.
    }









     private void SaveMessageToQueue(string m)
        {

        IList<string> messageQueue = (List<string>)HttpContext.Current.
Session["LUMessages"];
        messageQueue.Add(m);
         }

Answer 1

This is because you have enable the Session and the Session lock all the calls until they return.

You can read also this question: Replacing ASP.Net's session entirely

also read: https://stackoverflow.com/a/3660837/159270