Question

I have an asp.net website to manage projects. I realized that when I click for the next project really fast and often it overrides all the next projects with the data of the first one. I call a method to save before to go for the next project. I use also a session variable for the id of the project.

EDIT:

It looks like the sever stacks the save method and the ids but keeps the values of the first project in the controls

Am I right?

this is the ajax that calls a server method to get the id and set it in an hidden field:

function NextClick() {
            var tabvalue = $("#<%=TabsToFocus.ClientId%>").val();
            $.ajax(
                {
                    type: "POST",
                    url: "Projet.aspx/NextProj",
                    data: "{tab:'" + tabvalue + "'}",
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function(d) {
                        if (d.d != "False") {
                            $("#<%=hid_selProjetID.ClientID%>").val(d.d);
                            var btn = $("#<%=btnClickLstProjet.ClientID%>");
                            fillHidden();
                             btn.click();
                        }
                    }
                });
            }

And btn.click() calls this method on the server side to save

Private Sub Button1_ServerClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnClickLstProjet.ServerClick

    If HttpContext.Current.Session.Item("isUser") IsNot Nothing AndAlso HttpContext.Current.Session.Item("isUser") = True Then
        If HttpContext.Current.Session.Item("curProjetID") IsNot Nothing Then

            btnSaveIndicateurs_Click()
            btnSaveEnTete_Click()
            btnSaveGen_Click()
            btnSavePlanif_Click()
        End If
    End If

    HttpContext.Current.Session.Item("curProjetID") = hid_selProjetID.Value
    Response.Redirect("Projet.aspx")

End Sub

Thank you

Answer 1

The very first thing you should do is STOP using session.

Seriously, back away from the session object.

A proper use of session is long term, fairly unchanging data. Data that has to change on literally every post back etc belongs in the page itself.

---

Here is what’s happening.

1. You click on a link to load up the project. The Session variable is being set with the current project id.

2. You then click on a link to get the next project,

3. Then quickly click on the link to get the one after that.

The server, meanwhile, is multithreaded. #3 basically interupted #2’s execution.. and ran before #2. This means your session variable is jacked up.

Why would the 3rd request run before the 2nd? Well, you are executing a number of queries. It’s likely that the queries for request 2 are taking slightly longer to exec than the ones for request 3.

Solution: Stop using Session.

Why: You cannot predict the order in which IIS is going to respond to requests. IIS is a parallel (not serial) engine and requests might very well happen out of the sequence you think they should.

Finally, the guy who said that session is locked by the first requestor wasn’t entirely accurate. It is WRITE locked.. but that only occurs when the page starts writing to session. Reads are not locked.

So, when request 3 executes it is using the ID of request 1, or 2. Depending on which one is still active by the time it hits the write code.