DataTables AJAX不调用服务器端方法

Question

我正在尝试在ASP.NET网络表单中实现DataTables.Net Server side。

$('#GridViewClient').dataTable({                
    stateSave: true,
    Processing: true,
    serverSide: true,
    ajax: "22.aspx/GetAllUsers"                
});


[WebMethod]    
public static string GetAllUsers()
{
    string sResult = "";

    try
    {
        BussinessLayer.Client obj = new BussinessLayer.Client();

        int nDraw = Convert.ToInt32(HttpContext.Current.Request.Params["draw"]);
        List<Client_table> lst = obj.GetAllClient();

        ReturnData oResult = new ReturnData();
        oResult.draw = nDraw;
        oResult.recordsTotal = lst.Count;
        oResult.recordsFiltered = lst.Count;

        foreach (Client_table o in lst)
            oResult.data.Add(o.ToString());

        sResult = oResult.ToString();


    }
    catch (Exception err)
    {
        string sMsg = err.Message;
        sResult = "";
    }

    return sResult;
}

当我尝试使用普通的ajax调用来调用此方法时，它工作正常并且调试点也在命中。但是当我使用datatables ajax请求调用此方法时，该方法没有被调用？