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  • 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/

     1         /// <summary>
     2         /// 添加
     3         /// </summary>
     4         /// <returns></returns>
     5         public static int Add()
     6         {
     7             using (var db = new NorthwindEntities())
     8             {
     9                 var customer = new Customers()
    10                 {
    11                     CustomerID = "fanguza",
    12                     Address = "地球",
    13                     City = "广东",
    14                     Phone = "13800138000",
    15                     CompanyName = "博客园",
    16                     ContactName = "反骨仔"
    17                 };
    18 
    19                 //方法一
    20                 //db.Customers.Add(customer);
    21 
    22                 //方法二
    23                 var entry = db.Entry(customer);
    24                 entry.State = EntityState.Added;
    25 
    26                 return db.SaveChanges();
    27             }
    28         }

     1         /// <summary>
     2         /// 删除
     3         /// </summary>
     4         /// <returns></returns>
     5         static int Delete()
     6         {
     7             using (var db = new NorthwindEntities())
     8             {
     9                 var customer = new Customers()
    10                 {
    11                     CustomerID = "fanguzi"
    12                 };
    13 
    14                 db.Customers.Attach(customer);
    15                 db.Customers.Remove(customer);
    16 
    17                 return db.SaveChanges();
    18             }
    19         }

     1         /// <summary>
     2         /// 编辑(修改)
     3         /// </summary>
     4         /// <returns></returns>
     5         static int Edit()
     6         {
     7             using (var db = new NorthwindEntities())
     8             {
     9                 var customer = db.Customers.FirstOrDefault(u => u.CustomerID == "fanguzai");
    10 
    11                 if (customer == null)
    12                 {
    13                     return 0;
    14                 }
    15 
    16                 customer.ContactName = "erwuzai";
    17                 return db.SaveChanges();
    18             }
    19         }

     1         /// <summary>
     2         /// 查询
     3         /// </summary>
     4         static Customers Query()
     5         {
     6             using (var db = new NorthwindEntities())
     7             {
     8                 var query =
     9                     db.Customers.Where(u => u.ContactName == "fanguza").OrderBy(u => u.ContactName).Take(1);
    10 
    11                 return query.FirstOrDefault();
    12             }
    13         }

    分页

     1         public IQueryable<Customers> GetPageOfCustomerses<TKey>(int pageIndex, int pageSize,
     2             Expression<Func<Customers, bool>> wherExpression,
     3             Expression<Func<Customers, TKey>> orderByExpression)
     4         {
     5             using (var db = new NorthwindEntities())
     6             {
     7                 //分页前需要排序
     8                 return db.Customers.Where(wherExpression).OrderBy(orderByExpression).Skip((pageIndex - 1) * pageSize).Take(pageSize);
     9             }
    10         }

    批量增加

     1         static void BatchAdd()
     2         {
     3             using (var db = new NorthwindEntities())
     4             {
     5                 for (var i = 0; i < 50; i++)
     6                 {
     7                     var customer = new Customers()
     8                     {
     9                         CustomerID = "fanguzai" + i,
    10                         Address = "中国",
    11                         City = "广州",
    12                         Phone = "13800138000" + i,
    13                         CompanyName = "阳春一中",
    14                         ContactName = "反骨仔" + i
    15                     };
    16 
    17                     db.Customers.Add(customer);
    18                 }
    19 
    20                 db.SaveChanges();
    21             }
    22         }

    其它

    1         public IQueryable<Customers> GetCustomerses<TKey>(Expression<Func<Customers, bool>> whereExpression,
    2             Expression<Func<Customers, TKey>> orderExpression)
    3         {
    4             using (var db = new NorthwindEntities())
    5             {
    6                 return db.Customers.Where(whereExpression).OrderBy(orderExpression);
    7             }
    8         }
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  • 原文地址:https://www.cnblogs.com/liqingwen/p/6555281.html
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