CodeFirst 用中文说是代码优先,此技术可以让我们先写代码,然后由Entity Framework根据我们的代码建立数据库
接下来用学生这个例子来演示,有学生表,课程表,和成绩表三张表
首先是Model层
学生表
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/**/
using System.ComponentModel.DataAnnotations;//验证namespace CodeFirstDemo.Models
{
public class Student
{
[Key]
public int Id { get; set; }
[Required]
[StringLength(50)]
public string Name { get; set; }
}
}
课程表
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/**/
using System.ComponentModel.DataAnnotations;//验证namespace CodeFirstDemo.Models
{
public class Course
{
[Key]
public int Id { get; set; }
[Required]
[StringLength(50)]
public string Name { get; set; }
}
}
成绩表
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/**/
using System.ComponentModel.DataAnnotations;//验证
namespace CodeFirstDemo.Models
{
public class Score
{
[Key]
public int Id { get; set; } public Student Student { get; set; } public Course Course { get; set; } }
}
[Key]表示在数据库中该字段为主键,[Required]表示不为空,[StringLength]也就是长度了
这一步完成之后,我们要建立一个StudentInfoEntities的类,这个类要继承自DbContext,而DbContext类在System.Data.Entity命名空间下,需引用EntityFramework.dll类库,
如安装不了,可以去Visual Studio Gallery下载,其实,只需要引用一个叫做Entity Framework的dll类库即可
StudentInfoEntities类
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
/**/
using System.Data.Entity;namespace CodeFirstDemo.Models
{
public class StudentInfoEntities:DbContext
{
public DbSet<Course> Courses { get; set; }
public DbSet<Score> Scores { get; set; }
public DbSet<Student> Students { get; set; }
}
}
接着,我们在Web.Config里配置一下数据库的连接字符串
<connectionStrings>
<add name="StudentInfoEntities" connectionString="Data Source=.\SQLEXPRESS; User=test;Password=test;Initial Catalog=StudentInfo;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
最后,新建一个HomeController
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
/**/
using CodeFirstDemo.Models;
namespace CodeFirstDemo.Controllers
{
public class HomeController : Controller
{
private StudentInfoEntities db = new StudentInfoEntities();
public string Index()
{
var data = db.Students.ToList();
return "Database is build success!";
} }
}
点击调试,触发一下,查看数据库
同时,您会发现,在Score表中,自动产生外键关系