C# DataTable 3种 Distinct 方法

//1.根据Order_No、Client_Code 两个字段去重，distinct之后的table只保留括号内写的字段
DataTable DtHeadDis = DtEntities.DefaultView.ToTable(true, "Order_No", "Client_Code")

//2.根据字段Ord_OrderNo去重，字段可以加，distinct之后的table保留全字段
var dt=DtHeadNow.AsEnumerable().ToList();
DataTable DtNewHead = dt.Where((x, i) => dt.FindIndex(z => z["Ord_OrderNo"] == x["Ord_OrderNo"]) == i).CopyToDataTable();

//3.手动筛选
DataTable DtHeadDis = DtHead.Clone();
            foreach (DataRow item in DtHead.Rows)
            {
              DataRow[] drs=  DtHeadDis.Select("Client_Code='" + item["Client_Code"].ToString() + "' and Order_No='" + item["Order_No"].ToString() + "'");
                if (drs.Count() == 0)
                {
                    DtHeadDis.ImportRow(item);
                }
            }
            foreach (DataRow Row in DtHeadDis.Rows)
            {
                Row.AcceptChanges();
                Row.SetAdded();
            }