在GridView 的 Footer 顯示總和－Gino的筆記本

最近在學C#，這對於我這個原本寫VB的人實在是很痛苦，語法差好多呀!最近遇到一個問題，就是將資料呈現在GridView後要顯是加總，於是上網找了一下有類似的範例改寫一下就完成囉!

以下是程式碼,紅色字體的部分就是囉!

protected void Button1_Click(object sender, EventArgs e)
        {

            StringBuilder sbSql = new StringBuilder();
            sbSql.Append("SELECT start_time,ani,phone_number,duration,total_units ");
            sbSql.Append("FROM billingrecorduser ");
            sbSql.Append("ORDER BY start_time");

            db_conn connectdb = new db_conn();
            SqlConnection oConn = connectdb.opendb("db201");
            SqlCommand cmd = new SqlCommand(sbSql.ToString() , oConn);

            try

                 {
                     oConn.Open();
                     SqlDataReader dr = cmd.ExecuteReader();

                     DataTable dt = new DataTable();
                     dt.Clear();

                     for (int i = 0; i <= dr.FieldCount - 1; i++)
                     {
                         DataColumn col = new DataColumn();
                         col.ColumnName = dr.GetName(i);
                         col.DataType = dr.GetFieldType(i);
                         dt.Columns.Add(col);
                     }

                     float nTotalDuration = 0;
                     float nTotalUnits = 0;

                     while (dr.Read())
                     {
                         DataRow row = dt.NewRow();

                         for (int j = 0; j <= dr.FieldCount - 1; j++)
                         {
                             row[j] = dr.GetValue(j);

                             if (j == 3)
                             {
                                 nTotalDuration = nTotalDuration + Convert.ToSingle(dr.GetSqlValue(j).ToString());

                             }

                             if (j == 4)
                             {
                                 nTotalUnits = nTotalUnits + Convert.ToSingle(dr.GetSqlValue(j).ToString());

                             }

                         }

                         dt.Rows.Add(row);
                     }

                     GridView1.DataSource = dt;
                     GridView1.DataBind();

                     GridView1.FooterRow.Cells[2].Text = "Total:";
                     GridView1.FooterRow.Cells[3].Text = nTotalDuration.ToString() ;
                     GridView1.FooterRow.Cells[4].Text = nTotalUnits.ToString();

                     dr.Close();
                     oConn.Close();


                }

                  catch (Exception ex)


                 {
                     Response.Write(ex.Message);
                 }



        }