Call Back to server

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ASP.NET

Javascript

Ajax

I'm trying to create a program that keeps a session open if a user is typing in a textbox. Below is the basic ASP.NET code:

<asp:TextBox ID="txtMemoBox" runat="server" OnKeyUp="javascript:ProcessKeyStroke();"></asp:TextBox>
<asp:TextBox ID="hField" runat="server" Text="0"></asp:TextBox>

txtMemoBox is the field that when the user is typing within it we want to keep the session open.

hField will be hidden and is used to count every 20 keystroke within the txtMemoBox field to determine when to renew the session. Therefore if 20 keystrokes haven't been detected within the given session time then the session will automatically expire.

Below is the javascript function ProcessKeyStroke():

function ProcessKeyStroke()
{
  document.getElementById('<%=hField.ClientID%>').value = parseFloat(document.getElementById('<%=hField.ClientID%>').value) + 1;

            if(document.getElementById('<%=hField.ClientID%>').value > 20)
            {
                document.getElementById('<%=hField.ClientID%>').value = 0;

                if (window.XMLHttpRequest)
                {// code for IE7+, Firefox, Chrome, Opera, Safari
                    xmlhttp = new XMLHttpRequest();
                }
                else
                {// code for IE6, IE5
                    xmlhttp = new ActiveXObject();
                }
            }
        }

I understand that XMLHttpRequest() allows calls to and from the server for individual controls. My question is does XMLHttpRequest() and ActiveXObject() alone communicate with the server and therefore renew the session?