CopyToDataTable()、SetField()

1、用查询创建数据表

 static void UseCopyToDataTable() {
            DataSet ds = BuildOneDTDataSet();//数据源
            DataTable student = ds.Tables["PeopleDt"];
            DataTable score = ds.Tables["Scores"];
            var query = from stu in student.AsEnumerable()
                        from sco in score.AsEnumerable()
                        where stu.Field<int>("Age") > 20 && stu.Field<int>("ScoreID") == sco.Field<int>("ScoreID")
                        select stu;
            foreach (var item in query)
            {
                Console.WriteLine("学生{0},年龄{1}，性别{2}", item.Field<string>("Name"), item.Field<int>("Age"), item.Field<string>("XingBie"));
            }
            DataTable cnstudent = query.CopyToDataTable();
            foreach (var item in cnstudent.AsEnumerable())
            {
                Console.WriteLine("学生{0},年龄{1}，性别{2}", item.Field<string>("Name"), item.Field<int>("Age"), item.Field<string>("XingBie"));
            }
        }

实际开发中CopyToDataTable通常用于界面绑定。

2、修改表中数据字段

static void UseSetField() {
            DataSet ds = BuildOneDTDataSet();
            DataTable dt = ds.Tables["PeopleDt"];
            foreach (var item in dt.AsEnumerable())
            {
                int age=item.Field<int>("Age");
                item.SetField<int>("Age",age+2);
                   Console.WriteLine("学生{0},年龄{1}，性别{2}", item.Field<string>("Name"), item.Field<int>("Age"), item.Field<string>("XingBie"));
            }

            DataTable dt2 = ds.Tables["PeopleDt"];
            foreach (var item in dt2.AsEnumerable())
            {
                Console.WriteLine("学生{0},年龄{1}，性别{2}", item.Field<string>("Name"), item.Field<int>("Age"), item.Field<string>("XingBie"));
            }

            DataSet ds2 = BuildOneDTDataSet();
            DataTable dt3 = ds2.Tables["PeopleDt"];
            foreach (var item in dt3.AsEnumerable())
            {
                Console.WriteLine("学生{0},年龄{1}，性别{2}", item.Field<string>("Name"), item.Field<int>("Age"), item.Field<string>("XingBie"));
            }
        
        }

由此可见SetFiled()修改的是Dataset中的数据，如果要保持元数据不变，要么在SetFiled()之前先备份数据表使用CopyToDataTable()，要么另起一个DataSet 对象