EF4支持三种构建方法：1. Database First方法。2.Model First方法。3.Code First 方法。开发人员可根据具体的项目情况，选择任一种方法。

上次快速演示了Model First的方法。这次演示Code First方法。

EF4.0引入CTP4可支持Code First了。Microsoft在EF4.1中引入EntityFramework4.1/4.2加强Code First的支持。（EF4.1的DataAnnotation, Fluent API 更完善，对POCO的支持更直接方便。关于EF4.1/4.2的使用，我在后面博文中我会补上的。）

在此，给出EF4.0的使用方法以快速演示：

首先，我们要下载并安装CTP4：URL 。

当安装完成CTP4后。（安装CTP4之前最好把Visual Studio2010关掉。）

1. 启动Visual Studio 2010.

2. 创建一个Console Application : 名称：EFCodeFirstWalkthrough

3. 在解决方案上右键，选择：添加一个类库项目：名称：EFCodeFirstWalkthroughModel。

4. 右键EFCodeFirstWalkthrough项目，添加.NET类库引用：Microsoft.Data.Entity.CTP; 添加.NET类库引用：System.Data.Entity.添加项目引用:EFCodeFirstWalkthroughModel.

5.在类库项目中添加类文件：Author.cs，Book.cs，Person.cs，Publisher.cs：代码如下：

1 Author 2  using System; 3  using System.Collections.Generic; 4  using System.Linq; 5  using System.Text; 6   7  namespace EFCodeFirstWalkthroughModel 8  { 9      public class Author : Person10      {   11          public int AuthorId { get; set; }12          public virtual ICollection
       
         Books { get; set; }13      }14  }
       

1 Book 2  using System; 3  using System.Collections.Generic; 4  using System.Linq; 5  using System.Text; 6   7  namespace EFCodeFirstWalkthroughModel 8  { 9      public class Book10      {11          public string ISBN { get; set; }12          public string Title { get; set; }13          public DateTime FirstPublished { get; set; }14          public bool IsFiction { get; set; }15          public virtual Publisher Publisher { get; set; }16          public virtual Author Author { get; set; }17      }    18  }

using System; using System.Collections.Generic; using System.Linq; using System.Text;  namespace EFCodeFirstWalkthroughModel {     public class Person     {         public int PersonId { get; set; }         public string FirstName { get; set; }         public string LastName { get; set; }     } }

using System; using System.Collections.Generic; using System.Linq; using System.Text;  namespace EFCodeFirstWalkthroughModel {     public class Publisher     {         public int PublisherId { get; set; }         public string Name { get; set; }         public virtual ICollection
       
         Books { get; set; }     }  }
       

 

6.在Cosole 项目EFCodeFirstWalkthrough 中添加类文件：BookCatalog.cs，BookConfiguration.cs ，并修改Program.cs 的代码。如下：

 

using System; using System.Collections.Generic; using System.Linq; using System.Text; using EFCodeFirstWalkthroughModel; using System.Data.Objects; using System.Data.EntityClient;   namespace EFCodeFirstWalkthrough {     public class BookCatalog : ObjectContext     {         private ObjectSet
       
         _books;         private ObjectSet
        
          _people;         private ObjectSet
         
           _publishers;          public BookCatalog(EntityConnection connection)             : base(connection)         { }          public ObjectSet
          
            Books         {             get             {                 return this._books == null                     ? this._books = this.CreateObjectSet
           
            ()                     : this._books;             }         }                  public ObjectSet
            
              People { get { return this._people == null ? this._people = this.CreateObjectSet
             
              () : this._people; } } public ObjectSet
              
                Publishers { get { return this._publishers == null ? this._publishers = this.CreateObjectSet
               
                () : this._publishers; } } } }
               
              
             
            
           
          
         
        
       

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.Entity.ModelConfiguration;  namespace EFCodeFirstWalkthroughModel {     public class BookConfiguration : EntityConfiguration
       
             {         public BookConfiguration()         {             this.HasKey(b => b.ISBN);             this.Property(b => b.Title).IsRequired();             this.HasRequired(b => b.Author).WithMany(a => a.Books);         }     } }
       

using System; using System.Collections.Generic; using System.Linq; using System.Text; using EFCodeFirstWalkthroughModel; using System.Data.Entity.ModelConfiguration; using System.Data.SqlClient;  namespace EFCodeFirstWalkthrough {     class Program     {         static void Main(string[] args)         {             var builder = new ModelBuilder();             builder.Configurations.Add(new BookConfiguration());             builder.Entity
       
        ();             builder.Entity
        
         ().Property(p => p.Name).IsRequired().HasMaxLength(50);             var model = builder.CreateModel();             using (var connection = new SqlConnection(@"Server=.\SQLEXPRESS;Database=CodeFirstWalkthrough;Trusted_Connection=True;"))             {                 using (var context = model.CreateObjectContext
         
          (connection))                 {                     if (!context.DatabaseExists())                     {                         context.CreateDatabase();                     }                     var book = new Book                     {                         ISBN = "1111",                         Title = "Intro to Code First",                         FirstPublished = DateTime.Today,                         IsFiction = false,                         Author = new Author { FirstName = "Rowan", LastName = "Miller" },                         Publisher = new Publisher { Name = "EF Books" }                     };                     context.Books.AddObject(book);                     context.SaveChanges();                 }             }         }     } }
         
        
       

 

编译项目，执行。

然后观察数据库：会发现生成一个名为CodeFirstWalkthrough的数据库文件。并且在里面有数据表生成。

注意：在此项目演示过程中，我们并未指定SqlConnection所用的连接字符串，但是EF4会利用我们指定给SqlConnection的参数去生连接特定的数据库服务器，并生成数据库。

好了，Code First 先到这里吧。休息咯！！！