EF 的 CURD 操作

EF 的 CURD 操作

　　这里采用了数据库 Northwind，下载地址：https://northwinddatabase.codeplex.com/

增

        /// <summary>
        /// 添加
        /// </summary>
        /// <returns></returns>
        public static int Add()
        {
            using (var db = new NorthwindEntities())
            {
                var customer = new Customers()
                {
                    CustomerID = "fanguza",
                    Address = "地球",
                    City = "广东",
                    Phone = "13800138000",
                    CompanyName = "博客园",
                    ContactName = "反骨仔"
                };

                //方法一
                //db.Customers.Add(customer);

                //方法二
                var entry = db.Entry(customer);
                entry.State = EntityState.Added;

                return db.SaveChanges();
            }
        }

删

        /// <summary>
        /// 删除
        /// </summary>
        /// <returns></returns>
        static int Delete()
        {
            using (var db = new NorthwindEntities())
            {
                var customer = new Customers()
                {
                    CustomerID = "fanguzi"
                };

                db.Customers.Attach(customer);
                db.Customers.Remove(customer);

                return db.SaveChanges();
            }
        }

改

        /// <summary>
        /// 编辑（修改）
        /// </summary>
        /// <returns></returns>
        static int Edit()
        {
            using (var db = new NorthwindEntities())
            {
                var customer = db.Customers.FirstOrDefault(u => u.CustomerID == "fanguzai");

                if (customer == null)
                {
                    return 0;
                }

                customer.ContactName = "erwuzai";
                return db.SaveChanges();
            }
        }

查

        /// <summary>
        /// 查询
        /// </summary>
        static Customers Query()
        {
            using (var db = new NorthwindEntities())
            {
                var query =
                    db.Customers.Where(u => u.ContactName == "fanguza").OrderBy(u => u.ContactName).Take(1);

                return query.FirstOrDefault();
            }
        }

分页

        public IQueryable<Customers> GetPageOfCustomerses<TKey>(int pageIndex, int pageSize,
            Expression<Func<Customers, bool>> wherExpression,
            Expression<Func<Customers, TKey>> orderByExpression)
        {
            using (var db = new NorthwindEntities())
            {
                //分页前需要排序
                return db.Customers.Where(wherExpression).OrderBy(orderByExpression).Skip((pageIndex - 1) * pageSize).Take(pageSize);
            }
        }

批量增加

        static void BatchAdd()
        {
            using (var db = new NorthwindEntities())
            {
                for (var i = 0; i < 50; i++)
                {
                    var customer = new Customers()
                    {
                        CustomerID = "fanguzai" + i,
                        Address = "中国",
                        City = "广州",
                        Phone = "13800138000" + i,
                        CompanyName = "阳春一中",
                        ContactName = "反骨仔" + i
                    };

                    db.Customers.Add(customer);
                }

                db.SaveChanges();
            }
        }

其它

        public IQueryable<Customers> GetCustomerses<TKey>(Expression<Func<Customers, bool>> whereExpression,
            Expression<Func<Customers, TKey>> orderExpression)
        {
            using (var db = new NorthwindEntities())
            {
                return db.Customers.Where(whereExpression).OrderBy(orderExpression);
            }
        }