EntityFramework默认映射规则

我不太习惯通过CodeFirst去维护数据库（尽管这是未来实现自动编程的必经之路），还是喜欢通过数据库设计工具如PowerDesigner去建表。如果不想对EF的实体和数据表做什么映射的话，就要注意默认映射规则。以订单表（Order）和订单明细表（OrdersDetails）这类一对多的关系表为例。

数据库建表脚本：

create table Orders
(
 id int primary key identity(1,1),
 OrderNo nvarchar(30),
 TotalAmount decimal(10,2),
 OrderTime datetime default getdate()
)

create table OrdersDetails
(
    id int primary key identity(1,1),
    Orders_Id int,
    Product_Id int,
    ProductName nvarchar(30),
    AddTime datetime default getdate()
)


create table Product
(
id int primary key identity(1,1),
name nvarchar(30),
)


insert into Orders(OrderNo,TotalAmount) values('001',500);
insert into Orders(OrderNo,TotalAmount) values('002',800);
insert into Orders(OrderNo,TotalAmount) values('003',1000);
insert into Orders(OrderNo,TotalAmount) values('004',560);
insert into Orders(OrderNo,TotalAmount) values('005',900);

insert into OrdersDetails(Orders_Id,Product_Id,ProductName) values(1,1,'Iphone8');
insert into OrdersDetails(Orders_Id,Product_Id,ProductName) values(1,2,'MI6');
insert into OrdersDetails(Orders_Id,Product_Id,ProductName) values(2,3,'HW7');
insert into OrdersDetails(Orders_Id,Product_Id,ProductName) values(3,4,'MZ');

insert into Product(Name) values('Iphone8');
insert into Product(Name) values('MI6');
insert into Product(Name) values('HW7');
insert into Product(Name) values('MZ');

View Code

总结的几个规则：

1.明细表的表明要用复数形式即 OrdersDetails

2.外键关系要 关联表名称_Id：Orders_Id，即使实体类是OrdersId也是去查找Orders_Id列

3.除了关联外键外其他字段最好用驼峰式命名，不要包含_或-

 

实体类和DbContext如下：

public class OrderManamgerDBContext : DbContext
    {
        public DbSet<Orders> Orders { get; set; }
        public DbSet<OrdersDetails> OrdersDetails { get; set; }

        public OrderManamgerDBContext() { }
        public OrderManamgerDBContext(string connectionString) : base(connectionString) { }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new OrdersDetailsConfiguration());

            base.OnModelCreating(modelBuilder);
        }
    }

    public class OrdersDetailsConfiguration : EntityTypeConfiguration<OrdersDetails>
    {
        public OrdersDetailsConfiguration()
        {
            //不是按照EF默认规则命名的需要手动映射
            //HasEntitySetName("OrdersDetails");
            //Property(t => t.OrdersId).HasColumnName("Orders_Id");
            //Property(t => t.ProductId).HasColumnName("Product_Id");
        }
    }

    public class Orders
    {
        public int id { get; set; }
        public string OrderNo { get; set; }
        public decimal TotalAmount { get; set; }
        public DateTime OrderTime { get; set; }
        public List<OrdersDetails> OrdersDetail { get; set; }
    }

    public class OrdersDetails
    {
        public int id { get; set; }
        public int Orders_Id { get; set; }
        public int Product_Id { get; set; }
        public string ProductName { get; set; }
        public DateTime AddTime { get; set; }
    }

View Code

 

如果实体类和数据表字段命名方式不一样就需要手动映射：

 public class OrdersDetail
    {
        public int id { get; set; }
        public int OrdersId { get; set; }
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public DateTime AddTime { get; set; }
    }

View Code

这个时候就要把DbContext中的注释放开

 

控制台程序，采用积极加载方式：

class EFTest
    {
        static OrderManamgerDBContext odmdb = new OrderManamgerDBContext("DbContext");
        //static OrderManamgerDBContext odmdb = new OrderManamgerDBContext(ConfigurationManager.ConnectionStrings["DbContext"].ConnectionString);
        public static void Main(string[] args)
        {
            

            var rlt=odmdb.Orders.Include("OrdersDetail").Where(od=>od.id==1);

            //var rlt = odmdb.Orders.Where(od => od.id == 1);

            foreach(var itm in rlt)
            {
                Console.WriteLine("单据编号 "+itm.OrderNo + "\r\n明细产品:");
                foreach (var citm in itm.OrdersDetail)
                {
                    Console.WriteLine(citm.ProductName);
                }
            }

            string sql = rlt.ToString();

            Console.Read();
        }
    }

View Code

 

建议能按照默认规则设计就按照默认规则设计，EF的一个初衷就是减少工作量

 

posted on 2018-01-26 14:20 好好学习V天天向上 阅读(…) 评论(…) 编辑 收藏

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