Ajax async call Asp.net not giving proper output

Question

I have two ajax calls that I would expect to behave asynchronously

        var toDate = '<%=ucChartDateSelector1.ToDate%>';
        var fromdate = '<%=ucChartDateSelector1.FromDate%>';
        var reportFor = '<%=ucChartDateSelector1.ddlReportType.SelectedItem.Text%>';
        var periodFor = '<%=ucChartDateSelector1.ddlDateSelection.SelectedItem.Text%>';

        $(document).ready(function () {
               GenerateChartReport();
        });

        function GenerateChartReport() {
            $.ajax({
                type: 'POST',
                url: 'Dashboard.aspx/ReadBooking',
                contentType: 'application/json',
                dataType: 'json',
                async: true,
                data: JSON.stringify({ fromDate: fromdate, toDate: toDate, reportFor: reportFor, periodFor: periodFor }),
                success: function (response) {
                    TwoColumnReport(response.d, "chartLine_div", "Google Dealy Example");

                },
                error: function (error) {
                    console.log(error);
                }

            }),
            $.ajax({
                type: 'POST',
                url: 'Dashboard.aspx/GetData', 
                contentType: 'application/json',
                dataType: 'JSON',
                async: true,
                success: function (response) {
                    TwoColumnReport(response.d, "visualization", "Google Charts Example");
                },
                error: function (error) {
                    console.log(error);
                }

            });

            return false;
        }
        function TwoColumnReport(dataValues, mainDivId, reportTitle) {
            var data = new google.visualization.DataTable();
            data.addColumn('string', 'Column Name');
            data.addColumn('number', 'Column Value');

            for (var i = 0; i < dataValues.length; i++) {
                data.addRow([dataValues[i].ColumnName, dataValues[i].Value]);
            }
            new google.visualization.PieChart(document.getElementById(mainDivId)).
               draw(data, { title: reportTitle });
        }

In the Server Side , I have following code. One function has a delay of 2 seconds and the other function has delay of 5 seconds.

[WebMethod]
public static List<Data> GetData()
{
    logger.WriteInfoLog(String.Format("***********GetData Start**********    "));
    int milliseconds = 2000;
    Thread.Sleep(milliseconds);
    List<Data> dataList = new List<Data>();

    dataList.Add(new Data("Column 1", 100));
    dataList.Add(new Data("Column 2", 200));
    dataList.Add(new Data("Column 3", 300));
    dataList.Add(new Data("Column 4", 400));
    logger.WriteInfoLog(String.Format("*********GetData End**********"));
    return dataList;
}

[WebMethod]
public static List<Data> ReadBooking(String fromDate, String toDate, String reportFor, String periodFor)
{
    logger.WriteInfoLog(String.Format("---------ReadBooking Summary Start.   Report type {0}-{3}  DateRange {1}- {2}----- ", reportFor, fromDate, toDate, periodFor));
    int milliseconds = 5000;
    Thread.Sleep(milliseconds);
    List<Data> dataList = new List<Data>();

    dataList.Add(new Data("row 1", 1400));
    dataList.Add(new Data("row 2", 3200));
    dataList.Add(new Data("row 3", 3100));
    dataList.Add(new Data("row 4", 4100));
    dataList.Add(new Data("row 5", 2400));
    logger.WriteInfoLog(String.Format("---------ReadBooking Summary. End----- "));
    return dataList;
}

I expect the log to be in following order:

 --------ReadBooking Summary Start.   Report type Weekly -11 Jan 2016 
   DateRange 11/01/2016 12:00:00 AM- 17/01/2016 12:00:00 AM-----  
   ***********GetData Start**********
        *********GetData End********** 
       ---------ReadBooking Summary. End-----

But the output I am getting is:

 ---------ReadBooking Summary Start.   Report type Weekly -11 Jan 2016  DateRange 11/01/2016 12:00:00 AM- 17/01/2016 12:00:00 AM----- 
---------ReadBooking Summary. End----- 
***********GetData Start**********
*********GetData End**********

What am I missing?

Did you check the network tab on dev tool for execution of Ajax call?check if second ajax call is made immediately after first or after 5seconds? — pratikpawar
– pratikpawar, Commented Jan 14, 2016 at 22:21
you might want to check the other questions similar to the issue. It seems asp.net session processes requests in queue. check this out stackoverflow.com/questions/4428413/… — pratikpawar
– pratikpawar, Commented Jan 14, 2016 at 22:28
I'm a bit away from ASP.NET nowadays but it seems that the Thread.Sleep()call stops the entire script for the given time. Both calls are fired, but the first one is locking the second one out. Maybe because both running on the same thread. — Tyr
– Tyr, Commented Jan 14, 2016 at 22:28
In NetworkTab, its showing that both started Same time. But the log is not in the way expected. May be thread may have kept the log writing locked !! — makdu
– makdu, Commented Jan 14, 2016 at 22:56

Community · Accepted Answer · 2017-05-23 10:27:56Z

0

In ASP.NET, if two requests are made from the same session they get exclusive access to the SessionState, aka they run sequentially, not in parallel.

In your example, they both get fired at the same time, but whichever one arrives second gets put in the queue until the first one is finished, because they are both from the Session (based on the SessionId).

You can circumvent the problem by applying the following attribute to your controller:

[SessionState(SessionStateBehavior.Disabled)]

Of course, you won't be able to access the HttpContext.Current.Session property (well, you can, but it will be null)

More references:

https://msdn.microsoft.com/en-us/library/ms178581.aspx (see the part about Concurrent Requests and Session State)
Why would multiple simultaneous AJAX calls to the same ASP.NET MVC action cause the browser to block?
Asynchronous Controller is blocking requests in ASP.NET MVC through jQuery

edited May 23, 2017 at 10:27

CommunityBot

11 silver badge

answered Jan 15, 2016 at 0:21

Kenneth

28.8k7 gold badges65 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

makdu Over a year ago

Vow, you have clarified my doubt that even though they got fired together, the reason why logs not happen in same time . I will check the suggestion given by you

makdu Over a year ago

I am using Webforms and cannot disable sessionstate as i am using session variables in code

Kenneth Over a year ago

If you can't disable session state, unfortunately there's not other way around it.

Collectives™ on Stack Overflow

Ajax async call Asp.net not giving proper output

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related