Entity Framework Code First 系列 2——Hello World Code first

Code First 我来了

现在我们从头开始一步一步创建一个基于Code First 模式的应用程序，看仔细了！

1. 创建类库项目，使用Nuget导入Entity framework (建议大家都是用Nuget来管理dll)，或者直接引入entityframework.dll 我使用的版本是4.3

 

2. 在visual studio 新增建模项目,当然你也可以不需要,不过通过可视化建模可以通过T4模板自动生成领域模型类（需安装额外的visual studio 功能包）,我们建立三个领域实体分别是学校(School) 班级(Classroom) 学生(Student)

 

 

在安装visual studio  可视化建模功能包后 点击右键可以看见成长代码的选项，自动生成的代码示例如下：

 

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     Changes to this file will be lost if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

namespace Stephen.Sample.AEF.CodeFirstSample.Domain
{
    public class Student
    {
        public string StudentId
        {
            get;
            set;
        }

        public string StudentName
        {
            get;
            set;
        }

        public bool StudentSex
        {
            get;
            set;
        }

        public int StudentAge
        {
            get;
            set;
        }

    }
}

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     Changes to this file will be lost if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System.Collections.Generic;

namespace Stephen.Sample.AEF.CodeFirstSample.Domain
{
    public class School
    {
        public string SchoolId
        {
            get;
            set;
        }

        public string SchoolName
        {
            get;
            set;
        }

        public virtual List<Classroom> Classrooms
        {
            get;
            set;
        }

        public virtual Address Adrress
        {
            get;
            set;
        }

    }
}

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     Changes to this file will be lost if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System.Collections.Generic;

namespace Stephen.Sample.AEF.CodeFirstSample.Domain
{
    public class Classroom
    {
        public string ClassroomId
        {
            get;
            set;
        }

        public string ClassName
        {
            get;
            set;
        }

        public virtual List<Student> Students
        {
            get;
            set;
        }

    }
}

3.创建DbContext

  

 

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using Stephen.Sample.AEF.CodeFirstSample.Domain.DBConfiguration;

namespace Stephen.Sample.AEF.CodeFirstSample.Domain.DBContext
{
    public class SchoolDbContext : DbContext
    {
        public DbSet<School> Schools { get; set; }
        public DbSet<Classroom> Classrooms { get; set; }
        public DbSet<Student> Students { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new StudentConfiguration());
            modelBuilder.Configurations.Add(new AddressConfiguration());
        }
    }
}

 

 ok 这样一个最简单EntityFramwork Codefirst Application 就诞生了。

4. 测试

默认情况下 entityframework 会找到本地默认的SQLEXPRESS 数据实例创建数据因此可以不用配置数据库.

创建后运行即可得到初始化后的数据库表(包括主外键关系和初始数据)

 [TestMethod]
        public void InitSchoolDBTestMethod()
        {
            using (var schoolDb = new SchoolDbContext())
            {

                Database.SetInitializer(new DropCreateDatabaseIfModelChanges<SchoolDbContext>());
                schoolDb.Schools.Add(MockSchool());
                schoolDb.SaveChanges();
            }
        }