Gridview without datasource

[Sylviarabi]

Hi
I am wokrin on a website where i hav a grid view displaying data from an SQL table accordin to the customer chosen in the dropdown list in the update panel.

This works fine but i am havin trouble with the sorting when i click on the column name.Also paging does not work.The following are the functions i used:

private string GridViewSortDirection
        {
        get { return ViewState["SortDirection"] as string ?? "ASC"; }
        set { ViewState["SortDirection"] = value; }
        }
        private string GridViewSortExpression
        {
        get { return ViewState["SortExpression"] as string ?? string.Empty; }
        set { ViewState["SortExpression"] = value; }
        }
        private string GetSortDirection()
        {
       switch (GridViewSortDirection)
            {
                case "ASC":
                GridViewSortDirection = "DESC";
                break;
                case "DESC":
                GridViewSortDirection = "ASC";
                break;
            }
             return GridViewSortDirection;
        }
        protected void GridViewOrders_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
        GridViewOrders.DataSource = SortDataTable(GridViewOrders.DataSource as DataTable, true);
        GridViewOrders.PageIndex = e.NewPageIndex;
        GridViewOrders.DataBind();
        if (GridViewOrders.Rows.Count == 0)
        {
            NoData.Visible = true;
        }
        else
        {
            NoData.Visible = false;
        }
        }
        protected DataView SortDataTable(DataTable dataTable, bool isPageIndexChanging)
        {
        if (dataTable != null)
            {
                DataView dataView = new DataView(dataTable);
               if (GridViewSortExpression != string.Empty)
                {
                   if (isPageIndexChanging)
                    {
                       dataView.Sort = string.Format("{0} {1}", GridViewSortExpression, GridViewSortDirection);
                   }
                   else
                    {
                       dataView.Sort = string.Format("{0} {1}", GridViewSortExpression, GetSortDirection());
                   }
               }
               return dataView;
           }
           else
            {
               return new DataView();
           }
       }
       protected void GridViewOrders_Sorting(object sender, GridViewSortEventArgs e)
        {
           GridViewSortExpression = e.SortExpression;
           int pageIndex = GridViewOrders.PageIndex;
           GridViewOrders.DataSource = SortDataTable(myDataSet.Tables[0] as DataTable, false);
           GridViewOrders.DataBind();
           GridViewOrders.PageIndex = pageIndex;
       }
 
and i have mentioned abt the functions in the gridview as follows:
 
<asp:GridView ID="GridViewOrders" runat="server" AutoGenerateColumns="False" Width="900px"
                AllowSorting="True" AllowPaging="True" PageSize="20" PagerSettings-NextPageText="Next" OnPageIndexChanging="GridViewOrders_PageIndexChanging"  
OnSorting="GridViewOrders_Sorting" >

PLease help me with this.I am a beginner so i would need detailed solution.Thanks in advance.