一、前言
1、本教程主要内容
- ASP.NET Core MVC 集成 EF Core 介绍&操作步骤
- ASP.NET Core MVC 使用 EF Core + Linq to Entity 访问MySQL数据库
- ASP.NET Core MVC 使用 EF Core + 原生SQL访问MySql数据库
- EF Core + MySQL数据库插入数据后获取自增列的值
Entity Framework Core 简称为 EF Core
2、本教程环境信息
| 软件/环境 | 说明 |
|---|---|
| 操作系统 | Windows 10 |
| SDK | 2.1.401 |
| ASP.NET Core | 2.1.3 |
| MySQL | 8.0.x |
| IDE | Visual Studio Code 1.30 |
| 浏览器 | Chrome 70 |
| VS Code插件 | 版本 | 说明 |
|---|---|---|
| C# | 1.17.1 | 提供C#智能感知， .NET Core 调试、编译等 |
| vscdoe-solution-explorer | 0.3.1 | 提供解决方案视图 |
本篇代码以下代码进行调整：https://github.com/ken-io/asp.net-core-tutorial/tree/master/chapter-02
3、准备工作
安装MySQL数据库：https://dev.mysql.com/downloads/mysql/
- Windows环境
下载安装包后双击安装，一直下一步即可。
- MacOS环境
参考：https://ken.io/note/macos-mysql8-install-config-tutorial
- CentOS环境
参考：https://ken.io/note/centos-mysql8-setup
4、前置知识
- 控制反转（IOC）原则与依赖注入（DI）
ASP.NET Core 默认集成了DI。所有官方模块的引入都要使用DI的方式引入。
https://baike.baidu.com/item/IOC
- Linq使用教程
https://docs.microsoft.com/zh-cn/dotnet/csharp/tutorials/working-with-linq
二、EF Core + MySQL 前置准备
EF Core 全称：Entity Framework Core，为微软为 .NET Core平台开发的ORM框架。对应是 .NET Framework平台的 Entity Framework（EF），无论是EF还是EF Core都可以说是 .NET 平台开发效率最高的ORM框架。
1、引入 EF Core + MySQL Provider
EF Core已经集成在 ASP.NET Core 中，但默认并不支持MySQL，如果需要连接MySQL,需要添加MySQL相关的Provider，这里我选择的是：Pomelo.EntityFrameworkCore.MySql
任意命令行操作即可，我用的是VS Code自带的命令行
//进入项目根目录： Ken.Tutorial.Web
cd Ken.Tutorial.Web
//添加Package
dotnet add package Pomelo.EntityFrameworkCore.MySql
这里我添加的 MySql.Data.EntityFrameworkCore 版本是 8.0.13，如果你想跟我使用一样的版本，可以使用以下命令：
dotnet add package Pomelo.EntityFrameworkCore.MySql --version 2.1.4
2、创建MySQL库表
- 创建数据库
CREATE DATABASE ken_tutorial;
- 创建表
USE ken_tutorial;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
`hobby` varchar(500) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
3、配置链接字符串
在项目根目录Ken.Tutorial.Web中创建配置文件appsettings.json,并写入以下配置
{
"ConnectionStrings": {
"testdb": "server=localhost;database=Ken.Tutorial;uid=root;pwd=root;"
}
}
4、实体&DbContext准备
创建user表对应实体
在项目根目录Ken.Tutorial.Web中创建目录Models,并在其中创建类：UserEntity.cs
using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace Ken.Tutorial.Web.Models
{
[Table("user")]
[Serializable]
public class UserEntity
{
[Key]//主键
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]//自增列
[Column("id")]
public int Id { get; set; }
[Column("name")]
public string Name { get; set; }
[Column("age")]
public int Age { get; set; }
[Column("hobby")]
public string Hobby { get; set; }
}
}
创建DBContext
在项目根目录Ken.Tutorial.Web中创建目录Repositories,并在其中创建类：TutorialDbContext.cs
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
namespace Ken.Tutorial.Web.Repositories
{
public class TutorialDbContext : DbContext
{
private IConfiguration Configuration { get; }
public TutorialDbContext(IConfiguration configuration)
{
this.Configuration = configuration;
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseMySql(Configuration.GetConnectionString("testdb"));
}
ppublic DbSet Users { get; set; }
}
}
TutorialDbContext 继承了 DbContext，然后再Context初始化时配置MySQL链接。
由于 ASP.NET Core 默认使用了DI组件，所以我们取配置文件，就需要在构造函数中获取
IConfiguration注入的实例。
在Startup.cs配置注入，以便数据访问类可以访问DI方式获取TutorialDbContext
public void ConfigureServices(IServiceCollection services)
{
//引入MVC模块
services.AddMvc();
//配置DbContext注入
services.AddTransient();
}
三、EF Core + Linq to entity 访问数据库
1、创建Linq To Entity 数据访问类
using System;
using System.Collections.Generic;
using System.Linq;
using Ken.Tutorial.Web.Models;
namespace Ken.Tutorial.Web.Repositories
{
public class TutorialRepository
{
private TutorialDbContext DbContext { get; }
public TutorialRepository(TutorialDbContext dbContext)
{
//在构造函数中注入DbContext
this.DbContext = dbContext;
}
//添加
public int Add(UserEntity user)
{
using (DbContext)
{
//由于我们在UserEntity.Id配置了自增列的Attribute，EF执行完成后会自动把自增列的值赋值给user.Id
DbContext.Users.Add(user);
return DbContext.SaveChanges();
}
}
//删除
public int Delete(int id)
{
using (DbContext)
{
var userFromContext = DbContext.Users.FirstOrDefault(u => u.Id == id);
DbContext.Users.Remove(userFromContext);
return DbContext.SaveChanges();
}
}
//更新
public int Update(UserEntity user)
{
using (DbContext)
{
var userFromContext = DbContext.Users.FirstOrDefault(u => u.Id == user.Id);
userFromContext.Name = user.Name;
userFromContext.Age = user.Age;
userFromContext.Hobby = user.Hobby;
return DbContext.SaveChanges();
}
}
//查询
public UserEntity QueryById(int id)
{
using (DbContext)
{
return DbContext.Users.FirstOrDefault(u => u.Id == id);
}
}
//查询集合
public List QueryByAge(int age)
{
using (DbContext)
{
return DbContext.Users.Where(u => u.Age == age).ToList();
}
}
//查看指定列
public List QueryNameByAge(int age)
{
using (DbContext)
{
return DbContext.Users.Where(u => u.Age == age).Select(u => u.Name).ToList();
}
}
//分页查询
public List QueryUserPaging(int pageSize, int page)
{
using (DbContext)
{
return DbContext.Users.Skip(pageSize * (page - 1)).Take(pageSize).ToList();
}
}
//事务：将年龄<0的用户修改年龄为0
public int FixAge()
{
using (DbContext)
{
using (var transaction = DbContext.Database.BeginTransaction())
{
try
{
var userListFromContext = DbContext.Users.Where(u => u.Age < 0);
foreach (UserEntity u in userListFromContext)
{
u.Age = 0;
}
var count = DbContext.SaveChanges();
transaction.Commit();
return count;
}
catch
{
transaction.Rollback();
return 0;
}
}
}
}
}
}
2、创建测试API
在Controllers文件夹下创建EfCoreController.cs作为访问入口
using System;
using Ken.Tutorial.Web.Models;
using Ken.Tutorial.Web.Repositories;
using Microsoft.AspNetCore.Mvc;
namespace Ken.Tutorial.Web.Controllers
{
public class EfCoreController : Controller
{
public TutorialRepository Repository { get; }
public EfCoreController(TutorialRepository repository)
{
this.Repository = repository;
}
public IActionResult Add(UserEntity user)
{
var message = Repository.Add(user) > 0 ? "success" : "failed";
return Json(new { Message = message, User = user });
}
public IActionResult Delete(int id)
{
var message = Repository.Delete(id) > 0 ? "success" : "failed";
return Json(new { Message = message });
}
public IActionResult Update(UserEntity user)
{
var message = Repository.Update(user) > 0 ? "success" : "failed";
return Json(new { Message = message, User = user });
}
public IActionResult QueryById(int id)
{
var user = Repository.QueryById(id);
return Json(new { User = user });
}
public IActionResult QueryByAge(int age)
{
var users = Repository.QueryByAge(age);
return Json(new { Users = users });
}
public IActionResult QueryNameByAge(int age)
{
var users = Repository.QueryNameByAge(age);
return Json(new { Users = users });
}
public IActionResult QueryUserPaging(int pageSize, int page)
{
var users = Repository.QueryUserPaging(pageSize, page);
return Json(new { Users = users });
}
public IActionResult FixAge()
{
var count = Repository.FixAge();
return Json(new { FixCount = count });
}
}
}
3、启动测试
- 在Startup.cs中配置Repository注入
public void ConfigureServices(IServiceCollection services)
{
//其他代码省略
//配置Repository注入
services.AddTransient();
}
- 启动项目并测试
| API | 示例 |
|---|---|
| 添加用户 | /efcore/add?name=ken&age=18&hobby=coding |
| 删除用户 | /efcore/delete?id=0 |
| 更新用户 | /efcore/update?id=1&name=ken&age=666&hobby=codingOrGaming |
| 查询单个用户 | /efcore/querybyid?id=0 |
| 查询多个用户 | /efcore/querybyage?age=18 |
| 查询多个用户名 | /efcore/querynamebyage?age=18 |
| 分页查询用户 | /efcore/queryuserpaging?pagesize=3&page=1 |
| 修复异常年龄 | /efcore/fixage |
四、EF Core + 原生SQL 访问数据库
1、创建EF Core + 原生SQL 数据访问类
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using Ken.Tutorial.Web.Models;
using Microsoft.EntityFrameworkCore;
using MySql.Data.MySqlClient;
namespace Ken.Tutorial.Web.Repositories
{
public class TutorialWithSqlRepository
{
private TutorialDbContext DbContext { get; }
public TutorialWithSqlRepository(TutorialDbContext dbContext)
{
//在构造函数中注入DbContext
this.DbContext = dbContext;
}
//添加
public int Add(UserEntity user)
{
using (var connection = DbContext.Database.GetDbConnection())
{
connection.Open();
var command = connection.CreateCommand() as MySqlCommand;
command.CommandText = "INSERT INTO user (name,age,hobby) VALUES(@name,@age,@hobby)";
command.Parameters.Add(new MySqlParameter()
{
ParameterName = "@name",
DbType = DbType.String,
Value = user.Name
});
command.Parameters.Add(new MySqlParameter()
{
ParameterName = "@age",
DbType = DbType.Int32,
Value = user.Age
});
command.Parameters.Add(new MySqlParameter()
{
ParameterName = "@hobby",
DbType = DbType.String,
Value = user.Hobby
});
var count = command.ExecuteNonQuery();
//获取插入时产生的自增列Id并赋值给user.Id使用
user.Id = (int)command.LastInsertedId;
return count;
}
}
//删除
public int Delete(int id)
{
using (DbContext)
{
return DbContext.Database.ExecuteSqlCommand(
"DELETE FROM user WHERE id={0}", id);
}
}
//更新
public int Update(UserEntity user)
{
using (DbContext)
{
return DbContext.Database.ExecuteSqlCommand(
"UPDATE user SET name={0}, age={1}, hobby={2} WHERE id={3}",
user.Name, user.Age, user.Hobby, user.Id);
}
}
//查询
public UserEntity QueryById(int id)
{
using (DbContext)
{
return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user WHERE id={0}", id).FirstOrDefault();
}
}
//查询集合
public List QueryByAge(int age)
{
using (DbContext)
{
return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user WHERE age={0}", age).ToList();
}
}
//查看指定列
public List QueryNameByAge(int age)
{
using (DbContext)
{
return DbContext.Users.FromSql("SELECT id,name FROM user WHERE age={0}", age).Select(u => u.Name).ToList();
}
}
//分页查询
public List QueryUserPaging(int pageSize, int page)
{
using (DbContext)
{
return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user LIMIT {0},{1}", pageSize * (page - 1), pageSize).ToList();
}
}
//事务：将年龄<0的用户修改年龄为0
public int FixAge()
{
using (DbContext)
{
using (var connection = DbContext.Database.GetDbConnection())
{
//打开连接
connection.Open();
//开启事务
using (var transaction = connection.BeginTransaction())
{
try
{
//获取命令对象
var command = connection.CreateCommand();
command.Transaction = transaction;
command.CommandText = "UPDATE user SET age=@age WHERE age<@age";
command.Parameters.Add(new MySqlParameter()
{
ParameterName = "@age",
DbType = DbType.Int32,
Value = 0
});
var count = command.ExecuteNonQuery();
transaction.Commit();
return count;
}
catch (Exception ex)
{
connection.Close();
transaction.Rollback();
return 0;
}
}
}
}
}
}
}
2、创建测试API
在Controllers文件夹下创建EfCoreWithSqlController.cs作为访问入口
using System;
using Ken.Tutorial.Web.Models;
using Ken.Tutorial.Web.Repositories;
using Microsoft.AspNetCore.Mvc;
namespace Ken.Tutorial.Web.Controllers
{
public class EfCoreWithSqlController : Controller
{
public TutorialWithSqlRepository Repository { get; }
public EfCoreWithSqlController(TutorialWithSqlRepository repository)
{
this.Repository = repository;
}
public IActionResult Add(UserEntity user)
{
var message = Repository.Add(user) > 0 ? "success" : "failed";
return Json(new { Message = message, User = user });
}
public IActionResult Delete(int id)
{
var message = Repository.Delete(id) > 0 ? "success" : "failed";
return Json(new { Message = message });
}
public IActionResult Update(UserEntity user)
{
var message = Repository.Update(user) > 0 ? "success" : "failed";
return Json(new { Message = message, User = user });
}
public IActionResult QueryById(int id)
{
var user = Repository.QueryById(id);
return Json(new { User = user });
}
public IActionResult QueryByAge(int age)
{
var users = Repository.QueryByAge(age);
return Json(new { Users = users });
}
public IActionResult QueryNameByAge(int age)
{
var users = Repository.QueryNameByAge(age);
return Json(new { Users = users });
}
public IActionResult QueryUserPaging(int pageSize, int page)
{
var users = Repository.QueryUserPaging(pageSize, page);
return Json(new { Users = users });
}
public IActionResult FixAge()
{
var count = Repository.FixAge();
return Json(new { FixCount = count });
}
}
}
3、启动测试
- 在Startup.cs中配置Repository注入
public void ConfigureServices(IServiceCollection services)
{
//其他代码省略
//配置Repository注入
services.AddTransient();
}
- 启动项目并测试
| API | 示例 |
|---|---|
| 添加用户 | /efcorewithsql/add?name=ken&age=18&hobby=coding |
| 删除用户 | /efcorewithsql/delete?id=0 |
| 更新用户 | /efcorewithsql/update?id=1&name=ken&age=666&hobby=codingOrGaming |
| 查询单个用户 | /efcorewithsql/querybyid?id=0 |
| 查询多个用户 | /efcorewithsql/querybyage?age=18 |
| 查询多个用户名 | /efcorewithsql/querynamebyage?age=18 |
| 分页查询用户 | /efcorewithsql/queryuserpaging?pagesize=3&page=1 |
| 修复异常年龄 | /efcorewithsql/fixage |
五、备注
1、附录
- 本文代码示例
https://github.com/ken-io/asp.net-core-tutorial/tree/master/chapter-08
- 本文参考
https://docs.microsoft.com/zh-cn/ef/core
https://www.learnentityframeworkcore.com
https://mysql-net.github.io/MySqlConnector/tutorials/net-core-mvc/
本文首发于我的独立博客：https://ken.io/note/asp.net-core-tutorial-entity-framework-core-mysql