C#中datatabl加入两列数据

Question

怎么在itemData中把第8,9列中的数据插进去（diff1列的值为Num1，diff2列的值为Num2），初学者求解

        itemData.Columns[8].ColumnName = "diff1";
        itemData.Columns[9].ColumnName = "diff2";
        for(int i=0;i<itemData.Rows.Count;i++)
        {
            int a = int.Parse(itemData.Rows[i]["ITEMQTY"].ToString());
            int b = int.Parse(itemData.Rows[i]["NEWITEMQTY"].ToString());
            int c=int.Parse(itemData.Rows[i+1]["ITEMQTY"].ToString());
            string Num1 = (a - b).ToString();
            string Num2 = (b - c).ToString();

Answer 1

循环前面用itemData.Columns.Add()先添加两列