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 = "",
                     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 ;
                 }

                 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();

                 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 - ) * pageSize).Take(pageSize);
             }
         }

批量增加

         static void BatchAdd()
         {
             using (var db = new NorthwindEntities())
             {
                 for (var i = ; i < ; i++)
                 {
                     var customer = new Customers()
                     {
                         CustomerID = "fanguzai" + i,
                         Address = "中国",
                         City = "广州",
                         Phone = "" + 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);
             }
         }