public CartHandler()    {    }    public CartHandler(int id, int num, string action)    {        this.id = id;// string.IsNullOrEmpty(context.Request.Params["id"]) ? 0 : Convert.ToInt32(context.Request.Params["id"]);        this.num = num;// string.IsNullOrEmpty(context.Request.Params["num"]) ? 0 : Convert.ToInt32(context.Request.Params["num"]);        this.action = action;// string.IsNullOrEmpty(context.Request.Params["action"]) ? "" : context.Request.Params["action"];    }

if exists(select * from sysobjects where name =‘tr_student_insert‘)drop trigger tr_student_insertgocreate trigger tr_student_inserton student after insertas--declare @studentNo int =(select StudentNo from inserted)--declare @classId int =(select ClassId from inserted)declare @studentNo intdeclare @classId intselect @studentNo=studentNo, @classId= ClassId from insertedif((select ClassId from grade where ClassId=@classId) is null)beginprint ‘id不存在，删除一条插入的数据‘--delete Student where StudentNo=@studentNoendelseprint ‘id 存在，不做任何操作‘select * from insertedgoinsert Student values(‘123123‘,‘nnn‘,‘女‘,0,‘138‘,‘地址地址‘,‘2012-12-12‘,‘xx@qq.com‘,0)select * from Student