mvc 学习笔记

  ldcdbEntities db = new ldcdbEntities();

            //查询
            IQueryable<LDC_Goods_Brand> temp = from u in db.LDC_Goods_Brand
                                               where u.Id > 0
                                               select u;
            foreach (var item in temp)
            {
                Console.WriteLine(item.BrandName);

            }
            //修改
            //通过linq表达式 或者学的lamdba查询出来的 实体 ，默认是被Ef的上下为你监视的
            var GoodsBrand = temp.FirstOrDefault();
            if (GoodsBrand != null)
            {
                Console.WriteLine(GoodsBrand.BrandName);
                //内部会自动告诉上下文我单签的实体改变了 状态也一并改成Modified状态
                GoodsBrand.BrandName = DateTime.Now.ToString();
                //给上下文 下命令 ；去把所有的尸体变化保存回数据库
                db.SaveChanges();
            }
            //删除扫做
            if (GoodsBrand != null)
            {
                //db.LDC_Goods_Brand.删除操作没有成功！！！！！！
            }


            //添加
            LDC_Goods_Brand brand = new LDC_Goods_Brand();
            brand.BrandName = "新添加的！！";
            brand.CreateTime = DateTime.Now;
            db.LDC_Goods_Brand.Add(brand);//添加方法不同
            db.SaveChanges();
            Console.ReadKey();

 //查询部分列
            //var demo1 = from u in db.LDC_Goods_Brand
            //            select new { u.Id, u.BrandName };
            var demo2 = db.LDC_Goods_Brand.Where<LDC_Goods_Brand>(oo => oo.Id > 2).Select(oo => new { oo.Id, oo.BrandName });
            foreach (var item in demo2)

  //分页查询
            var demo4 = db.LDC_Goods_Brand.Where<LDC_Goods_Brand>(uu => uu.Id > 0)
                //.OrderBy<LDC_Goods_Brand, int>(uu => uu.Id);//升序
                .OrderByDescending(uu => uu.Id)//按照降序
                .Skip<LDC_Goods_Brand>(2)//越过多少条
                .Take<LDC_Goods_Brand>(2);//取多少条
            //命令式编程   函数式编程
            #endregion