引入

Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Design
Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Tools

DBFirst MsSqlServer

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="7.0.9" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="7.0.9">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="7.0.9" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="7.0.9">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>

测试DbFirst

User表

1.创建测试表

USE [DotNetCoreWeb]
GO
/****** Object:  Table [dbo].[User]    Script Date: 2023/7/17 17:45:39 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[User](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[Name] [nvarchar](50) NULL,
	[Age] [int] NULL,
	[Sex] [int] NULL,
	[Mobile] [nvarchar](50) NULL,
	[Emali] [nvarchar](50) NULL,
	[Address] [nvarchar](100) NULL,
	[Account] [nvarchar](50) NOT NULL,
	[Password] [nvarchar](50) NOT NULL,
 CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO

Nuget

1.使用Nuget控制台执行下面代码,需要替换连接字符串


Scaffold-DbContext "Data Source=192.168.1.11;Initial Catalog=DotNetCoreWeb;Persist Security Info=True;User ID=sa;Password=a123456789A..;TrustServerCertificate=true" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models -Force

测试

1.使用WebApi测试

using EntityFrameCoreWebApp.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore.ChangeTracking;

namespace EntityFrameCoreWebApp.Controllers
{
    [Route("api/[controller]/[action]")]
    [ApiController]
    public class UsersController : ControllerBase
    {
        DotNetCoreWebContext _context;
        public UsersController(DotNetCoreWebContext context)
        {
            _context = context;
        }
        [HttpGet]
        public IActionResult Get()
        {
            User user = _context.Users.First(it => it.Id == 1);
            return new JsonResult(user);
        }

        [HttpGet]
        public IActionResult GetById(int id)
        {
            User user = _context.Users.First(it => it.Id == id);
            return new JsonResult(user);
        }

        [HttpPost]
        public IActionResult Add(User user)
        {
            EntityEntry<User> result = _context.Users.Add(user);
            int ret = _context.SaveChanges();
            return new JsonResult(new { SaveChanges  = ret});
        }
    }
}

CodeFirst MsSqlServer

先备份
EnsureDeleted 有库则删除
EnsureCreated 创建

_context.Database.EnsureDeleted(); //删除
_context.Database.EnsureCreated(); //创建

保存原始数据并重新创建库

备份数据

public async Task<IActionResult> BackUpData()
{
    List<Role> roles = _context.Roles.ToList();
    string basepath = AppContext.BaseDirectory;
    XmlSerializer serializer = new XmlSerializer(typeof(List<Role>));

    using (FileStream fs = FileEx.Create(basepath + "Role.xml"))
    {
        serializer.Serialize(fs, roles);
    }

    await Task.CompletedTask;
    return new JsonResult(new { state = true});
}

在OnModelCreating增加

public void OnModelCreatingPartial(ModelBuilder modelBuilder)
{
    string backUpPath = AppContext.BaseDirectory + "Role.xml";
    if (File.Exists(backUpPath))
    {
        using (StreamReader sr = File.OpenText(backUpPath))
        {
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(List<Role>));
            List<Role>? roles = (List<Role>?)xmlSerializer.Deserialize(sr);
            if (roles != null && roles.Any()) 
            {
                modelBuilder.Entity<Role>().HasData(roles);
            }
        }
    }
}

执行codefirst

_context.Database.EnsureDeleted();
_context.Database.EnsureCreated();

迁移命令

类似于Git提交记录
1. 生成迁移文件add-migration 迁移文件名称 , 执行完会生成对应的 Migrations 文件夹
- add-migration db01
1. 更新或还原迁移文件到数据库update-database 迁移文件名称
- update-databse db01

打印日志

使用 UseLoggerFactory()方法

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder.UseSqlServer("Data Source=192.168.1.11;Initial Catalog=DotNetCoreWeb2;Persist Security Info=True;User ID=sa;Password=a123456789A..;TrustServerCertificate=true").UseLoggerFactory(LoggerFactory.Create(configure => configure.AddConsole()));
}

状态

Detached 未关联
Unchanged 有关联,但没有操作
Deleted 删除
Modified修改
Added 添加

执行删除的时候修改状态为其他状态将会执行对应的状态例:
- 下方代码并不会删除而是执行修改操作

User user = await dbContext.Users.FirstAsync(it => it.Name == "周杰伦");
dbContext.Users.Remove(user);
dbContext.Entry(user).State = EntityState.Modified;
user.Name = "刘德华";
dbContext.SaveChanges();

导航属性

有级联关系的可以创建导航属性如: User 和 Roel 用 RoleId 作为外键Id
在User类中增加 public virtual Role Role { get; set; } = null!; 为导航属性
在Role类中增加 public virtual ICollection Users { get; set; } = new List (); 为引用属性

贪婪加载

使用Include 可以将关联Role表的User数据全部加载出来
Role role = await dbContext.Roles.Include(it => it.Users).FirstAsync(it => it.Id == 7);

懒加载

第一种方式

引入
在生成的Context.cs => OnConfiguring(DbContextOptionsBuilder optionsBuilder) 中添加 optionsBuilder.UseLazyLoadingProxies() 这样查询的时候不会加载Role数据, 当需要的时候才会加载

第二种方式

在实体类中的构造函数使用 ILazyLoader loader 注入如:

ILazyLoader loader;
public User(ILazyLoader loader)
{
    this.loader = loader;
}
private Role _Role;
    public virtual Role Role
    {
        get
        {
            return loader!.Load(this, ref _Role!)!;
        }
        set
        {
            _Role = value;
        }
    }

设置查询状态不跟踪

有些时候不需要对查询的数据进行增删改, 所以去掉状态跟踪提升性能

全局设置

在生成的Context.cs的构造函数中添加
this.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;

局部设置

dbContext.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;

执行时设置

await dbContext.Roles.AsNoTracking().FirstAsync(it => it.Id == 7);