for (int i = 0; i < Headdt.Rows.Count; i++)            {                DataRow [] rows = Headdt.Select();                DataTable dt = new DataTable();                dt = rows[i].Table.Clone();                foreach (DataRow row in rows)                {                    dt.Rows.Add(row);  // 将DataRow添加到DataTable中//报错 该行已经属于另一个表。                }                
}求解啊