Datatabel操作 获取重复的数据

/// <summary>
        /// 获取对固定列不重复的新DataTable
        /// </summary>
        /// <param name="dt">含有重复数据的DataTable</param>
        /// <param name="colName">需要验证重复的列名</param>
        /// <returns>新的DataTable，colName列不重复</returns>
        private DataTable GetDistinctTable(DataTable dt,string colName)
        {
            DataView dv = dt.DefaultView;
            DataTable dtCardNo = dv.ToTable(true, colName);
            DataTable Pointdt = new DataTable();
            Pointdt = dv.ToTable();
            Pointdt.Clear();
            for (int i = 0; i < dtCardNo.Rows.Count; i  )
            {
                DataRow dr = dt.Select( colName + "='" + dtCardNo.Rows[ i ][ 0 ].ToString( ) + "'" )[ 0 ];
                Pointdt.Rows.Add(dr.ItemArray);
            }
            return Pointdt;
        }