I checked in temp table while inserting last selected record stored in the top tats y it s showing in 1st page of grid view how to solve this one

protected void grvMatGrp_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        Matflag = 1;
        grvMatGrp.PageIndex = e.NewPageIndex;
        GetMaterialList();
    }


public void GetMaterialList()
    {
        try
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Code");            
            dt.Columns.Add("CodeDesc");
            dt.Columns.Add("ShortCodeDesc");
            dt.Columns.Add("Type");
            
            DataTable dtTemp = new DataTable();
            dtTemp.Columns.Add("CodeTemp");
            dtTemp.Columns.Add("CodeDescTemp");
            dtTemp.Columns.Add("TypeTemp");
            DataTable DT = new DataTable();
            int rowcount = (grvMatGrp.PageIndex) * grvMatGrp.PageSize + grvMatGrp.Rows.Count;
            DataSet DS = new DataSet();
            DS = Session["lstSelected"] as DataSet;
            DT = DS.Tables[0];
            
            if (Matflag != 1)
                DT = DS.Tables[0];

            //else                                                 //Edited Regards The Paginators Not Working Bug
            //    DT = (DataTable)ViewState["CurrentTableData"];


            if (DT.Rows.Count > 0)
            {
                if (Matflag != 1)                               //Edited Regards The Paginators Not Working Bug
                   DT.Columns.Add("ShortCodeDesc");


                foreach (DataRow dr in DT.Rows)
                {
                    string str = string.Empty;
                    str = dr["CodeDesc"].ToString();
                    if (str.Length > 100)
                    {
                        str = str.Substring(0, 100) + " ...";
                    }
                    dr["ShortCodeDesc"] = str;
                }
            }

            if (grvMatGrp.Rows.Count == 0)
            {

                grvMatGrp.DataSource = DT;
                grvMatGrp.DataBind();
               
                Session["CurrentTableData"] = DT;

            }
             
            else
            {
               

                     foreach (GridViewRow row in grvMatGrp.Rows)
                     {
                         var Grv_Code = row.Cells[0].FindControl("grvlblMatGrpCode") as Label;
                         var Grv_CodeDesc = row.Cells[1].FindControl("grvlblMatGrp") as Label;
                         dt.Rows.Add(Grv_Code.Text, Grv_CodeDesc.Text);
                     }
                     for (int i = 0; i < DT.Rows.Count; i++)
                     {
                         string NewRecord = DT.Rows[i]["Code"].ToString();
                         char Present_Flag = 'N';
                         int count = 0;

                         foreach (DataRow dtRow in dt.Rows)
                         {
                             if (NewRecord != dtRow["Code"].ToString())
                             {
                                 Present_Flag = 'Y';
                             }
                             else
                             {
                                 count = count + 1;
                                 Present_Flag = 'N';
                             }
                         }

                         if (Present_Flag == 'Y' && count == 0)
                         {
                             DataRow NewRow = dtTemp.NewRow();
                             NewRow["CodeTemp"] = DT.Rows[i]["Code"].ToString();
                             NewRow["CodeDescTemp"] = DT.Rows[i]["CodeDesc"].ToString();
                             dtTemp.Rows.Add(NewRow);
                         }
                     }
                     if (dtTemp.Rows.Count != 0)
                     {
                         for (int N = 0; N < dtTemp.Rows.Count; N++)
                         {
                             DataRow NewRow = dt.NewRow();
                             NewRow["Code"] = dtTemp.Rows[N]["CodeTemp"].ToString();
                             NewRow["CodeDesc"] = dtTemp.Rows[N]["CodeDescTemp"].ToString();
                             dt.Rows.Add(NewRow);
                         }
                     }
                     if (dt.Rows.Count > 0)
                     {
                         if (dt.Columns.Contains("ShortCodeDesc") == false)
                         {
                             dt.Columns.Add("ShortCodeDesc");
                         }

                         foreach (DataRow dr in dt.Rows)
                         {
                             string str = string.Empty;
                             str = dr["CodeDesc"].ToString();
                             if (str.Length > 100)
                             {
                                 str = str.Substring(0, 100) + " ...";
                             }
                             dr["ShortCodeDesc"] = str;
                         }
                     }

                     if (dt.Rows.Count != 0)
                      {
                         
                              Session["CurrentTableData"] = dt;

                              grvMatGrp.DataSource = dt;
                              grvMatGrp.DataBind();
                          
                     }
                
            }
            pnlMatCart.Visible = false;
            pnlMatGrp.Visible = true;
           
            ControlEnable();
            updPnl.Update();
        }
        catch (Exception ex)
        {

        }

    }