1.首先新建 Asp.Net Core WebApi 项目

2.添加一下引用 ：

2.1   Pomelo.EntityFrameworkCore.MySql(我用的Mysql 根据自己情况引用就行)

2.2  Microsoft.EntityFrameworkCore

2.3 Microsoft.EntityFrameworkCore.Design

3.使项目支持dotnet ef 工具以使用Migrations

3.1 手动修改csproj文件(手动添加是因为在nuget添加Microsoft.EntityFrameworkCore.Tools.DotNet 时报错，估计是vs的问题)，添加一下配置

4.打开CMD命令 cd到项目目录下(C:\Users\Administrator\source\repos\CodeFirst\CodeFirst),执行

dotnet build

Microsoft (R) Build Engine version 15.1.545.13942 Copyright (C) Microsoft Corporation. All rights reserved. Startup.cs(45,13): warning CS4014: Because this call is not awaited, execution of the current method continues before the call is completed. Consider applying the 'await' operator to the result of the call. [C:\WorkSpacesC\DotNetCore\EntityFrameworkCoreMigrationsDemo\EntityFrameworkCoreMigrationsDemo\EntityFrameworkCoreMigrationsDemo.csproj] EntityFrameworkCoreMigrationsDemo -> C:\WorkSpacesC\DotNetCore\EntityFrameworkCoreMigrationsDemo\EntityFrameworkCoreMigrationsDemo\bin\Debug\netcoreapp1.0\EntityFrameworkCoreMigrationsDemo.dll Build succeeded. Startup.cs(45,13): warning CS4014: Because this call is not awaited, execution of the current method continues before the call is completed. Consider applying the 'await' operator to the result of the call. [C:\WorkSpacesC\DotNetCore\EntityFrameworkCoreMigrationsDemo\EntityFrameworkCoreMigrationsDemo\EntityFrameworkCoreMigrationsDemo.csproj] 1 Warning(s) 0 Error(s) Time Elapsed 00:00:04.76

5. 第4步完成后继续执行

dotnet ef

可以看见独角兽就说明引用成功了。距离胜利更近一步了

6.创建实例 StudentDbContext和相关实体类

usingCodeFirst.Model.Entity;usingMicrosoft.EntityFrameworkCore;usingSystem;usingSystem.Collections.Generic;usingSystem.Text;namespaceCodeFirst.Model.Db

{public classStudentDbContext: DbContext

{public StudentDbContext(DbContextOptionsoptions)

:base(options)

{

}protected override voidOnConfiguring(DbContextOptionsBuilder optionsBuilder)

{

optionsBuilder.UseMySql(@"Server=localhost;Port=3306;Database=Policy;UId=root;Pwd=mysql.com");

}public DbSet Student { get; set; }public DbSet Teacher { get; set; }

}

}

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.Text;namespaceCodeFirst.Model.Entity

{public classStudent

{

[Key]public int Id { get; set; }public string Name { get; set; }public Teacher Teach { get; set; }

}

}

usingSystem;usingSystem.Collections.Generic;usingSystem.Text;namespaceCodeFirst.Model.Entity

{public classTeacher

{public int Id { get; set; }public int Age { get; set; }public List Stus { get; set; }

}

}

7. 在Startup将StudentDbContext 注册为服务

8.使用Migrations  新建数据库初始化类DbInitializer

usingCodeFirst.Model.Db;usingMicrosoft.EntityFrameworkCore;usingSystem;usingSystem.Collections.Generic;usingSystem.Text;usingSystem.Threading.Tasks;namespaceCodeFirst.Model

{public classDbInitializer

{public voidInitializeAsync(StudentDbContext context)

{//var migrations = await context.Database.GetPendingMigrationsAsync();//获取未应用的Migrations，不必要，MigrateAsync方法会自动处理

context.Database.MigrateAsync();//根据Migrations修改/创建数据库

}

}

}

9.在Startup.cs的Configure方法中，添加参数StudentContext context，netcore会使用DI将DbContext注入到Configure方法，并添加对DbInitializer的调用。

10.使用dotnet ef命令创建Migrations：dotnet ef migrations add text  text随便起名

C:\Users\Administrator\source\repos\CodeFirst\CodeFirst>dotnet ef migrations add Initial

Build succeeded.0Warning(s)0Error(s)

Time Elapsed00:00:02.32Done. To undothis action, use 'ef migrations remove'

如果执行dotnet ef migrations add Initial报错 :

解决办法执行下面

定位到csproject

PM> dotnet ef migrations script --verbose -i --project "C:\Users\Administrator\source\repos\CodeFirst\CodeFirst"

完了继续操作就行

PM>add-migration test

PM>update-database

生成数据库表:

。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

修改Student实体类加一个Sex字段

public string Sex { get; set; }

执行 (注意执行命令之前在控制台‘默认项目’列表选中DbContext所在的类库，不然爆错)

Add-Migration ModifyStudent

再执行

PM> Update-Database

数据库已经更新

Demo源码: Github