.Net Core EntityFrameCore
目录
[*]引入
[*]DBFirst MsSqlServer
[*]测试DbFirst
[*]User表
[*]Nuget
[*]测试
[*]CodeFirst MsSqlServer
[*]保存原始数据并重新创建库
[*]备份数据
[*]在OnModelCreating增加
[*]执行codefirst
[*]迁移命令
[*]打印日志
[*]状态
[*]导航属性
[*]贪婪加载
[*]懒加载
[*]第一种方式
[*]第二种方式
[*]设置查询状态不跟踪
[*]全局设置
[*]局部设置
[*]执行时设置
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
GO
/****** Object:Table . Script Date: 2023/7/17 17:45:39 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE .(
IDENTITY(1,1) NOT NULL,
(50) NULL,
NULL,
NULL,
(50) NULL,
(50) NULL,
(100) NULL,
(50) NOT NULL,
(50) NOT NULL,
CONSTRAINT PRIMARY KEY CLUSTERED
(
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
) ON
GONuget
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
{
/")]
public class UsersController : ControllerBase
{
DotNetCoreWebContext _context;
public UsersController(DotNetCoreWebContext context)
{
_context = context;
}
public IActionResult Get()
{
User user = _context.Users.First(it => it.Id == 1);
return new JsonResult(user);
}
public IActionResult GetById(int id)
{
User user = _context.Users.First(it => it.Id == id);
return new JsonResult(user);
}
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
[*]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
[*]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);
来源:https://www.cnblogs.com/qfccc/archive/2023/07/19/17566770.html
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