EF中间表操作

Posted 2021-01-31 biao-123

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();

            }