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.net EFCore基本操作

作者：weixin_40725706 | 2024-03-17 02:36:34

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.net efcore

theme: smartblue

环境搭建

下载包

Microsoft.EntityFrameworkCore.SqlServer image.png

Microsoft.EntityFrameworkCore.Tools

image.png

创建实体类Book

``` using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;

namespace EFCore { public class Book { public int Id { get; set; }

  1. public string Title { get; set; }
  2.  
  3.     public DateTime PubTime { get; set; }
  4.  
  5.     public double Price { get; set; }
  6.  
  7. }

}

```

创建配置类

对应数据库表

``` using Microsoft.EntityFrameworkCore; using Microsoft.EntityFrameworkCore.Metadata.Builders; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;

namespace EFCore { public class BookConfig : IEntityTypeConfiguration { public void Configure(EntityTypeBuilder builder) { builder.ToTable("T_Books"); builder.Property(b=> b.Title) .HasMaxLength(50).IsRequired(); builder.Property(b=> b.AuthorName) .HasMaxLength(20).IsRequired(); } } }

```

对应数据库配置

``` using Microsoft.EntityFrameworkCore; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;

namespace EFCore { public class MyDBContext:DbContext { public DbSet Books { get; set; } 

  1. public DbSet<Person> Persons { get; set; }
  2.  
  3.     protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  4.     {
  5.         base.OnConfiguring(optionsBuilder);
  6.         optionsBuilder.UseSqlServer(
  7.             "server=.159.138.73;" +
  8.             "uid=SA;" +
  9.             "pwd=qwer1234.;" +
  10.             "database=demo1_Enviroment;" +
  11.             "TrustServerCertificate=true;"
  12.             );
  13.     }
  14.  
  15.     protected override void OnModelCreating(ModelBuilder modelBuilder)
  16.     {
  17.         base.OnModelCreating(modelBuilder);
  18.         // 从当前程序集加载所有的IEntityTypeConfiguration
  19.         modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
  20.     }
  21. }

}

```

Migration

初始化

显示控制台

image.png

控制台输入Add-Migration Init，初始化创表语句

image.png

控制台输入Update-Database，同步数据

image.png

image.png

添加修改

对 person 类添加了一个属性BirthPlace

控制台输入 Add-Migration AddBirth

image.png

Update-Database同步数据

image.png

Data Annotation

新增实体类cat

``` using System; using System.Collections.Generic; using System.ComponentModel.DataAnnotations; using System.ComponentModel.DataAnnotations.Schema; using System.Linq; using System.Text; using System.Threading.Tasks;

namespace EFCore { [Table("T_Cats")] public class Cat { public long Id { get; set; }

  1. [Required]
  2.     [MaxLength]
  3.     public string Name { get; set; }
  4. }

}

```

配置类添加cat

image.png

``` using Microsoft.EntityFrameworkCore; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;

namespace EFCore { public class MyDBContext:DbContext { public DbSet Books { get; set; } 

  1. public DbSet<Person> Persons { get; set; }
  2.  
  3.     public DbSet<Cat> Cats { get; set; }
  4.  
  5.     protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  6.     {
  7.         base.OnConfiguring(optionsBuilder);
  8.         optionsBuilder.UseSqlServer(
  9.             "server=192.159.138.73;" +
  10.             "uid=SA;" +
  11.             "pwd=qwer1234.;" +
  12.             "database=demo1_Enviroment;" +
  13.             "TrustServerCertificate=true;"
  14.  
  15.             );
  16.     }
  17.  
  18.     protected override void OnModelCreating(ModelBuilder modelBuilder)
  19.     {
  20.         base.OnModelCreating(modelBuilder);
  21.         // 从当前程序集加载所有的IEntityTypeConfiguration
  22.         modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
  23.     }
  24. }

}

```

Add-Migration addCat 和 Update-Database 后

image.png

增删改查

增

添加一条图书信息

namespace EFCore { public class Program { static async Task Main(string[] args) { // context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) { Book book = new Book(); book.Title = "西游记"; book.AuthorName = "吴承恩"; context.Books.Add(book); await context.SaveChangesAsync(); } } } }

image.png

查

已知有如下数据：

image.png

查询价格大于 80 的书籍信息

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. IQueryable<Book> books = context.Books.Where(b => b.Price > 80);
  2.             foreach(var book in books)
  3.             {
  4.                 await Console.Out.WriteLineAsync(book.Title+"__"+book.Price);
  5.             }
  6.             await context.SaveChangesAsync();
  7.         }
  8.     }
  9. }

} ```

image.png

查询"西游记"的作者

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. Book one = context.Books.Single(b => b.Title == "西游记");
  2.             await Console.Out.WriteLineAsync(one.AuthorName);
  3.  
  4.         }
  5.     }
  6. }

} ```

image.png

价格升序

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. IOrderedQueryable<Book> books = context.Books.OrderBy(b=>b.Price);
  2.             foreach (Book book in books)
  3.             {
  4.                 await Console.Out.WriteLineAsync(book.Title+","+book.Price);
  5.             }
  6.  
  7.         }
  8.     }
  9. }

} ``` image.png

按照作者名称分组，查询出版书籍数量以及售卖书籍最贵的价格

修改部分数据

image.png

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. var items = context.Books
  2.                 .GroupBy(b => b.AuthorName)
  3.                 .Select(g => new
  4.                 {
  5.                     Name = g.Key,
  6.                     BooksCount = g.Count(),
  7.                     MaxPrice = g.Max(b => b.Price)
  8.                 });
  9.             foreach(var item in items)
  10.             {
  11.                 await Console.Out.WriteLineAsync($"{item.Name},{item.BooksCount},{item.MaxPrice}");
  12.             }
  13.         }
  14.     }
  15. }

} ```

image.png

改

将西游记的作者修改为张三

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. Book book = context.Books.Single(b=>b.Title=="西游记");
  2.             book.AuthorName = "张三";
  3.             await context.SaveChangesAsync();
  4.  
  5.         }
  6.     }
  7. }

} ``` image.png

为所有价格大于10的书籍涨10块钱

涨价前

image.png

涨价后

image.png

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) { // context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) { IQueryable books = context.Books.Where(b => b.Price > 10); foreach(var b in books) { b.Price = b.Price + 10; } await context.SaveChangesAsync(); } } } }

```

删

删除编号为6的书籍

``` using System.Linq;

namespace EFCore { public class Program { static async Task Main(string[] args) {
// context 相当于逻辑上的数据库 using (MyDBContext context = new MyDBContext()) {

  1. Book book = context.Books.Single(b=>b.Id == 6);
  2.             context.Books.Remove(book);
  3.             await context.SaveChangesAsync();
  4.  
  5.         }
  6.     }
  7. }

} ```

image.png

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