.NET:Entity Framework 6.1笔记

EF6越来越完善，跟主流的Hibernate等ORM框架越来越接近了，先看下Entity类的定义：

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace EFSample.Model
{

    [Table("T_ORDER")]
    public class Order
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int ID { set; get; }

        [StringLength(50)]
        [Column("CUSTOMER_NAME")]
        public String CustomerName { set; get; }

        [Column("AMOUNT")]
        public decimal Amount { set; get; }

        public virtual ICollection<OrderItem> OrderItems { set; get; }

    }
}

 1 using System;
 2 using System.ComponentModel.DataAnnotations;
 3 using System.ComponentModel.DataAnnotations.Schema;
 4
 5 namespace EFSample.Model
 6 {
 7     [Table("T_ORDER_ITEM")]
 8     public class OrderItem
 9     {
10         [Key]
11         [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
12         public int ID { set; get; }
13
14         [ForeignKey("Order")]
15         [Column("ORDER_ID")]
16         public int OrderID { set; get; }
17
18         [StringLength(50)]
19         [Column("PRODUCT_NAME")]
20         public String ProductName { set; get; }
21
22         [Column("PRICE")]
23         public Decimal Price { set; get; }
24
25         [Column("QUANTITY")]
26         public int Quantity { set; get; }
27
28         public virtual Order Order { set; get; }
29
30
31     }
32 }

光看Attribute，已经跟Hibernate的Annotation很相似了。

配置文件：

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <configuration>
 3   <configSections>
 4     <section name="entityFramework"
 5        type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
 6   </configSections>
 7
 8   <entityFramework>
 9     <contexts>
10       <context type="EFSample.DAL.OrderContext, EFSample" disableDatabaseInitialization="false">
11         <databaseInitializer type="EFSample.DAL.OrderInitializer, EFSample" />
12       </context>
13     </contexts>
14     <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
15       <parameters>
16         <parameter value="v11.0" />
17       </parameters>
18     </defaultConnectionFactory>
19     <providers>
20       <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
21     </providers>
22   </entityFramework>
23
24   <startup>
25     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.1" />
26   </startup>
27
28   <connectionStrings>
29     <!--连接字符串，使用SQLSERVER LocalDb-->
30     <add name="MyConn" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=OrderDatabase;Integrated Security=SSPI;" providerName="System.Data.SqlClient" />
31   </connectionStrings>
32
33 </configuration>

注：LocalDb在开发阶段很方便，但是试用中有一个小问题，如果把生成的mdf物理文件删除后，再次运行总是报错(不知道是不是个别现象)，只能把Initial Catalog=OrderDatabase中的文件名改成其它名称（比如：Catalog=OrderDb），才能正常运行。

此外，NuGet Package Manager工具搞得象java的maven一样，可以自动联机下载所需的依赖项，Tools->NuGet Package Manager

输入

Install -Package EntityFramework

就能自动向project添加相关的dll引用

DbContext

 1 using EFSample.Model;
 2 using System.Data.Entity;
 3 using System.Data.Entity.ModelConfiguration.Conventions;
 4
 5 namespace EFSample.DAL
 6 {
 7     public class OrderContext:DbContext
 8     {
 9         public OrderContext() : base("MyConn") { }
10
11         public DbSet<Order> Orders { set; get; }
12
13         public DbSet<OrderItem> OrderItems { set; get; }
14
15         protected override void OnModelCreating(DbModelBuilder modelBuilder)
16         {
17             modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
18         }
19     }
20 }

示例代码：

 1 using EFSample.DAL;
 2 using EFSample.Model;
 3 using System;
 4 using System.Collections.Generic;
 5 using System.Linq;
 6
 7 namespace EFSample
 8 {
 9     class Program
10     {
11         static void Main(string[] args)
12         {
13             using (var db = new OrderContext())
14             {
15
16                 //直接执行Sql语句
17                 db.Database.ExecuteSqlCommand("delete from t_order");
18
19                 var orders = new List<Order>(){
20                     new Order{ CustomerName="jimmy.yang",Amount=200, OrderItems=new List<OrderItem>(){
21                         new OrderItem(){ Price=10, Quantity=20, ProductName="Mobile"}
22                     }},
23                     new Order{ CustomerName="杨俊明",Amount=300, OrderItems=new List<OrderItem>(){
24                         new OrderItem(){ Price=15, Quantity=20, ProductName="架构之美"}
25                     }}};
26
27                 //批量添加记录
28                 db.Orders.AddRange(orders);
29
30                 //提交到db
31                 db.SaveChanges();
32
33                 //查询
34                 var query = db.Orders.Where(c => c.CustomerName == "Jimmy.yang").AsQueryable();
35
36                 //输出Sql语句
37                 Console.WriteLine(query.ToString());
38
39                 List<Order> orderEntities = query.ToList();
40
41                 foreach (var order in orderEntities)
42                 {
43                     Console.WriteLine(String.Format("ID:{0}/CustomerName:{1}/Amount:{2}/ItemCount:{3}", order.ID, order.CustomerName, order.Amount,order.OrderItems.Count));
44                 }
45             }
46
47             Console.WriteLine("ok!");
48             Console.Read();
49         }
50     }
51 }

输出：

SELECT
[Extent1].[ID] AS [ID],
[Extent1].[CUSTOMER_NAME] AS [CUSTOMER_NAME],
[Extent1].[AMOUNT] AS [AMOUNT]
FROM [dbo].[T_ORDER] AS [Extent1]
WHERE N‘Jimmy.yang‘ = [Extent1].[CUSTOMER_NAME]

ID:9/CustomerName:jimmy.yang/Amount:200/ItemCount:1
ok!