GridView计算某一列的和 在最下面的一行显示

在GridView中增加了一个自动编号列
可以详细知道当前页一共有多少记录

int sumCl = 0;

            double sumMy = 0.00;

            for(int i=0;i<this.GridView1.Rows.Count;i++)

            {

                sumCl+= Convert.ToInt32(this.GridView1.Rows[i].Cells[5].Text.ToString());

                sumMy+= Convert.ToDouble(this.GridView1.Rows[i].Cells[6].Text.ToString());

            }

            if (e.Row.RowType == DataControlRowType.Footer)

            {

                e.Row.Cells[1].Text = "合计：";

                e.Row.Cells[5].Text = sumCl.ToString();

                e.Row.Cells[6].Text = sumMy.ToString();

            }