Ajax request in Web Browser Control working incorectly

I have a MVC web site with a httpGet function that do this

[HttpGet]
public JsonResult doSomething()
{
    if(Session[SessionName.count] == null) 
        Session[SessionName.count] = 0;

    Session[SessionName.count] += 1;
    retu Json(Session[SessionName.count], JsonRequestBehavior.AllowGet);
}

in the site there is a javascript function do this

function testing(){
    $.ajax({
        url: "@Url.Action("doSomething", "Test")",
        success: function (data) {
            alert(data);
        },
        error: function (data) {
            alert("error");
        }
    });
}

and finally in my web browser control

public void ShowCount() 
{
    browser.Document.InvokeScript("Testing");
}

everytime ShowCount() is call, the alert box in web browser control will always 1.