Issue using sAjaxSource and ASP.NET WebMethod

I am trying to create a datatable with server side paging on ASP.NET.

At first I tried to make use of the sAjaxSource without the the extra ajax (and used aoData.push for extra values). For some reason it did not work. I used fiddler to check what values it was sending.. everything seems correct but it does not return an error it just returns the whole page's HTML and the method is never called.

After searching around, i found that I can make an ajax call within fnServerData.. but now it seems like that is the only call made and values like "iDisplayLength" are not being sent over. That code is shown below.

Can anyone tell me how to do this please?

Thanks!

JS

logsTable = $('#grdEmailLogs').dataTable({
             "bProcessing": true,
             "bServerSide": true,
             "bFilter": false,
             "bSort": false,
             "bDestroy": true,
             "sAjaxSource": "Dashboard.aspx/LoadEmailsLogs",
             "fnServerData": function (sSource, aoData, fnCallback) {

                 // make ajax request, and assign request to variable
                 logsRequest = $.ajax({
                     type: "POST",
                     url: sSource,
                     data: "{ sender: '" + txtFilterSender.value + "', recipient: '" + txtFilterRecipient.value + "', subject: '" + txtFilterSubject.value + "', scanResult: '" + cmbFilterResult.options[cmbFilterResult.selectedIndex].value + "', fromFilterScanDateMils: '" + fromFilterScanDate + "', toFilterScanDateMils: '" + toFilterScanDate + "' }",
                     contentType: "application/json; charset=utf-8",
                     dataType: "json",
                     success: function (data) {
                         //var json = $.evalJSON(data.d);
                         fnCallback(data.d);
                     }
                 });
             },
             "sPaginationType": "full_numbers",
             "sPageButton": "paginate_button",
             "sPageButtonActive": "paginate_active",
             "sPageButtonStaticDisabled": "paginate_button"
         });

C#

[WebMethod]
        public static string LoadEmailsLogs(
            String sender,
            String recipient,
            String subject, 
            String scanResult,
            String fromFilterScanDateMils,
            String toFilterScanDateMils)
        {
            MasterClass.LogDebug("DashboardLogs::LoadLogs...", _cat);

            *CODE NOT SHOWN HERE*            

            string returnValue = "";

            try
            {
                FormatedList fl = new FormatedList();
                fl.sEcho = Convert.ToInt32(HttpContext.Current.Request.QueryString["sEcho"]);
                fl.SetData(dashboardLogs);
                fl.iTotalDisplayRecords = dashboardLogs.TotalLogsCount;
                fl.iTotalRecords = dashboardLogs.TotalLogsCount;
                fl.sColumns =
                    "icon," +
                    StringsProvider1.GetString("/DashboardLogs_ascx.SenderColumn") + "," +
                    StringsProvider1.GetString("/DashboardLogs_ascx.RecipientColumn") + "," +
                    StringsProvider1.GetString("/DashboardLogs_ascx.SubjectColumn") + "," +
                    StringsProvider1.GetString("/DashboardLogs_ascx.ScanResultColumn") + "," +
                    StringsProvider1.GetString("/DashboardLogs_ascx.ViewColumn");

                returnValue = new JavaScriptSerializer().Serialize(fl);

                MasterClass.LogDebug("--- returnValue - " + returnValue, _cat);
                //return fl;
            }
            catch (Exception ex)
            {
                MasterClass.LogError(ex.ToString(), _cat);
            }

            return returnValue;
        }