ASP.Net (C#) มีปัญหากับการแบ่งหน้า Gridview และหาผลรวมของแต่ละหน้าครับ

public partial class Default2 : System.Web.UI.Page
{
    SqlConnection objConn;
    Int16 Total2 = 0;
    //int num = 0;

    protected void Page_Load(object sender, EventArgs e)
    {
        
        if (Session["User"]!= null)
        {
            getdata();
            
        }
        else {
            Response.Redirect("Default3.aspx");
        }
    }
 
    protected void myDataGrid_PageIndexChanging(object sender, System.Web.UI.WebControls.GridViewPageEventArgs e)
    {
        myDataGrid.PageIndex = e.NewPageIndex;
        getdata();


    }

    public void getdata()
    {
        String strConnString;
        strConnString = "Server=10.11.1.17;UID=userreport;PASSWORD=gztr1998;database=DW01;Max Pool Size=400;Connect Timeout=600;";

        objConn = new SqlConnection(strConnString);
        objConn.Open();
        if (objConn.State == ConnectionState.Open)
        {
            this.lblText.Text = "SQL Server Connected";
        }
        else
        {
            this.lblText.Text = "SQL Server Connect Failed";
        }
        String Sql = "SELECT     [Doc Date], [Package Name], SUM([SMS Code Sent]) AS [SMS Code Sent],  SUM([SMS Payment-CS]) AS [Counter Service], SUM([PayDay-1]) AS [1 Day], SUM([PayDay-2]) AS [2 Days], SUM([PayDay-3]) AS [3 Days], SUM([PayDay-4]) AS [4 Days], SUM([PayDay-5]) AS [5 Days], SUM([PayDay-6]) AS [6 Days], SUM([PayDay-7]) AS [7 Days], SUM([PayDay-more7]) AS [more7], SUM([SMS Cancle]) AS [SMS Cancel] FROM   CEM_SMSCODE_Summary  where [DOC DATE] between '2013-05-21' and '2013-05-22' GROUP BY [Doc Date], [Package Name] ORDER BY [Doc Date], [Package Name]";
        SqlCommand com = new SqlCommand();
        com.Connection = objConn;
        com.CommandText = Sql;
        SqlDataReader dr = com.ExecuteReader();
        if (dr.HasRows)
        {
            DataTable dt = new DataTable();
            dt.Load(dr);
            myDataGrid.DataSource = dt;
            myDataGrid.DataBind();

        }

    }
    protected void myDataGrid_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e)
    {
        //if (e.Row.RowType == DataControlRowType.DataRow)
        //{
        //    num += Convert.ToInt32(e.Row.Cells[2].Text);
        //}
        //else if (e.Row.RowType == DataControlRowType.Footer)
        //{
        //    e.Row.Cells[2].Text = num.ToString();
        //}


        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            Total2 += Convert.ToInt16(DataBinder.Eval(e.Row.DataItem, "SMS Code Sent"));
        }
        else if (e.Row.RowType == DataControlRowType.Footer)
        {
            e.Row.Cells[0].Text = "Totals : ";
            e.Row.Cells[2].Text = Total2.ToString();
        }
    }
}