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
<ItemGroup> <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" /> </ItemGroup>
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
using CodeFirst.Model.Entity;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Text;
namespace CodeFirst.Model.Db
{
public class StudentDbContext: DbContext
{
public StudentDbContext(DbContextOptions<StudentDbContext> options)
: base(options)
{
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseMySql(
@"Server=localhost;Port=3306;Database=Policy;UId=root;Pwd=mysql.com");
}
public DbSet<Student> Student { get; set; }
public DbSet<Teacher> Teacher { get; set; }
}
}
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Text;
namespace CodeFirst.Model.Entity
{
public class Student
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public Teacher Teach { get; set; }
}
}
using System;
using System.Collections.Generic;
using System.Text;
namespace CodeFirst.Model.Entity
{
public class Teacher
{
public int Id { get; set; }
public int Age { get; set; }
public List<Student> 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
using CodeFirst.Model.Db;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
namespace CodeFirst.Model
{
public class DbInitializer
{
public void InitializeAsync(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.
0 Warning(s)
0 Error(s)
Time Elapsed 00:00:02.32
Done. To undo this action, use ‘ef migrations remove‘
如果执行dotnet ef migrations add Initial报错 :
解决办法执行下面两句
PM> dotnet ef Migrations add Init No project was found. Change the current working directory or use the --project option.
定位到csproject
完了继续操作就行
PM> add-migration test
PM> update-database
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
执行成功后，可以看到项目目录下多了个文件夹Migrations，里面就是自动生成的Migrations文件。
创建更新Migrations的命令跟创建初始的一样，只是最后一个参数自己定义即可。
最后执行代码，成功创建了新的数据库，并且里面有一个表__EFMigrationsHistory，是自动生成的用来记录Migrations记录。
修改Student类 public string NewField { get; set; }，在命令行执行命令dotnet ef migrations add NewField，然后运行程序，可以看到数据库已经更新，__EFMigrationsHistory表也多了一条对应的记录
生成数据库表:
Demo源码: Github
参考：https://www.cnblogs.com/yhnbgfd/p/6489278.html
原文地址：https://www.cnblogs.com/bin521/p/11697013.html