给DataTable添加序号列

如何在datatable中添加一序号列，编号从1依次递增，并且在第一列？

        /// <summary>
        /// 在DataTable中添加一序号列，编号从1依次递增
        /// </summary>
        /// <param >DataTable</param>
        /// <returns></returns>
        private DataTable AddSeriNumToDataTable(DataTable dt)
        {        
            //需要返回的值
            DataTable dtNew;
            if (dt.Columns.IndexOf("序号") >= 0)
            {
                dtNew = dt;
            }
            else //添加一序号列,并且在第一列
            {
                int rowLength = dt.Rows.Count;
                int  colLength= dt.Columns.Count;
                DataRow[] newRows = new DataRow[rowLength];

                dtNew = new DataTable();
                //在第一列添加“序号”列
                dtNew.Columns.Add("序号");
                for (int i = 0; i < colLength; i++)
                {
                    dtNew.Columns.Add(dt.Columns[i].ColumnName);
                    //复制dt中的数据
                    for (int j = 0; j < rowLength; j++)
                    {
                        if (newRows[j] == null)
                            newRows[j] = dtNew.NewRow();
                        //将其他数据填充到第二列之后，因为第一列为新增的序号列
                        newRows[j][i+1] = dt.Rows[j][i];
                    }
                }
                foreach (DataRow row in newRows)
                {
                    dtNew.Rows.Add(row);
                }

            }
            //对序号列填充，从1递增
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                dtNew.Rows[i]["序号"] = i + 1;
            }

            return dtNew;           
            
        }

        private DataTable dt;
        private void Form1_Load(object sender, EventArgs e)
        {
            dt = new DataTable();
            dt.Columns.Add("名称");
            dt.Columns.Add("价格");

            dt.Rows.Add("白菜", 12);
            dt.Rows.Add("白菜", 12);
            dt.Rows.Add("白菜", 12);
            dt.Rows.Add("白菜", 12);
            dt.Rows.Add("白菜", 12);

            DataTable dt2 = AddSeriNumToDataTable(dt);
            dataGridView1.DataSource = dt2;

        }