EF中间表操作

很久没用过ef了,最近换了公司,用的是ef框架,的确已经忘记了ef很多东西,虽说ef这东西性能不太好,但是可以满足我们的快速开发,在新的项目中我遇到了操作中间表的问题,我记得大学的时候用过,但是年代久矣,那时候又没有写博客的习惯,现在就写下来,以防又忘记了。

言归正传:

ef中间表是隐藏起来的,在ef可视化视图里面是看不到这个东东的。只能在数据库里面看到。

一共有3张表,如图下:

orders表是订单表,product是商品表,orders_product是中间表.

创建ef模型我就不说了,这个就略过了。

下面就开始操作中间表

一:新增:

public static void createfullordersbyproduct()
        {
            using (var dbcontext = new testentities())
            {
                var order = new orders
                {
                    ordertitle = "购买汽车",
                    customername = "sss",
                    transactiondate = datetime.now,
                    product = new list<product>()
                };
                var employee1 = new product { pname = "ss", orders = new list<orders>() };
                var employee2 = new product { pname = "sss", orders = new list<orders>() };
                dbcontext.orders.add(order);
                order.product.add(employee1);
                dbcontext.savechanges();
            }
        }

二:删除

 public static void emptyordersproduct()
        {
            using (var dbcontext = new testentities())
            {
                //获取product为1的所有orders所有的信息
                var producttoupdate = dbcontext.product.include("orders").firstordefault(x => x.id == 1);
                if (producttoupdate != null)
                {
                    producttoupdate.orders = new list<orders>();
                    dbcontext.savechanges();
                }
                else
                {
                    console.writeline("查询失败");
                }
            }
        }

//这也是新增 

public static void addordersproduct()
        {
            using (var dbcontext = new testentities())
            {
                var product = dbcontext.product.include("orders").firstordefault(x => x.id == 2);
                int[] orderlist = { 13, 14, 15, 16, 17, 18, 19 };
                if (product != null)
                {
                    var productorder = new hashset<int>(product.orders.select(x => x.id));
                    foreach (var item in dbcontext.orders)
                    {
                        if (productorder.contains(item.id))
                        {
                            //打印出重复的orderid
                            console.writeline("重复的id为" + item.id);
                            console.writeline("不执行添加结果");
                        }
                        else
                        {
                            //打印出employee表中没有id
                            console.writeline($"即将添加的值:{item.id}");
                            product.orders.add(item);
                        }
                    }
                }
                else
                {
                    console.writeline("product为空");
                }
                dbcontext.savechanges();
            }

        }

三:删除和修改

 public static void updateinfoproductorders()
        {
            using (var dbcontext = new testentities())
            {
                int[] orderidlist = { 13, 14, 15, 16, 17, 18, 19 };
                var productorders = dbcontext.product.include("orders").firstordefault(x => x.id == 2);
                if (productorders != null)
                {
                    //获取product中的orderlist
                    var productorderlist = new hashset<int>(productorders.orders.select(e => e.id));
                    foreach (var order in dbcontext.orders)
                    {
                        if (orderidlist.contains(order.id))
                        {
                            //判断要修改的orderid和orders表中的均包含
                            if (!productorderlist.contains(order.id))
                            {
                                console.writeline($"修改对应的订单id表{order.id}");
                                productorders.orders.add(order);
                            }
                        }
                        else
                        {
                            if (productorderlist.contains(order.id))
                            {
                                console.writeline($"删除无用的订单表{order.id}");
                                productorders.orders.remove(order);


                            }
                        }
                     
                    }
                }
                else
                {
                    console.writeline("查无的信息");
                }
                dbcontext.savechanges();

            }