DATATABLE中数据如何筛选重复数据

                    string[] temp = null;//存放已经入库的影片路径                    sql= "select originalName from DelFileList order by id desc";                    DataTable tb = db.getTable(sql);                    if (tb.Rows.Count > 0)                    ...{                        //对重复的数据进行筛选                        Hashtable ht = new Hashtable();                        foreach (DataRow dr in tb.Rows)                        ...{                            string s = dr["originalName"];                            if (!ht.Contains(s))                                ht[s] = dr["originalName"];                        }                        temp = new string[ht.Count];                        ht.Keys.CopyTo(temp, 0);                    }