EFCore入门建表,增删改查

安装两个NuGet:

Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Tools

1.创建一个Book.cs文件

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

namespace ConsoleApp2
{
    public class Book
    {
        public long Id { get; set; } //主键
        public string Title { get; set; } //标题
        public DateTime PubTime { get; set; } //发布日期
        public double Price { get; set; } //单价
        public string AuthorName { get; set; } //作者
    }
}

2.创建一个配置Book.cs文件的BookConfig.cs文件,如果进行配置,也可不创建

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 ConsoleApp2
{
    public class BookConfig : IEntityTypeConfiguration<Book>
    {
        public void Configure(EntityTypeBuilder<Book> builder)
        {
            builder.ToTable("T-Books"); //设置 Book和那一个表对应
            builder.Property(x => x.Title).HasMaxLength(50).IsRequired(); //IsRequired不能为空 //HasMaxLength最大长度
            builder.Property(s=>s.AuthorName).HasMaxLength(20).IsRequired(); //IsRequired不能为空 //HasMaxLength最大长度
            builder.Property(x => x.Name).HasColumnType("varchar(20)"); //HasColumnType指定数据类型
            //修改其它属性作为主键(默认Id作为主键使用)
            //builder.HasKey(x => x.Price);
            //设置默认值
            builder.Property(x => x.PubTime).HasDefaultValue(DateTime.Now);
            //设置唯一索引
            builder.HasIndex(x => x.Title).IsUnique();
            //设置符合索引
            builder.HasIndex(x => new { x.Name, x.AuthorName });

        }
    }
}

 

3,自定义一个文件,我这点取名MyDbContext.cs

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

namespace ConsoleApp2
{
    public class MyDbContext : DbContext
    {
        public MyDbContext(DbContextOptions<MyDbContext> options):base(options)
        {

        }
        public DbSet<Book> books { get; set; }
        //public DbSet<Person> persons { get; set; }
        //public DbSet<Dog> Dogs { get; set; }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
        }


        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            //从当前程序集里面加载所以的IEntityTypeConfiguration
            modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
        }

    }
}

4. 在Program.cs文件中注册DBContext

builder.Services.AddDbContext<MyDbContext>(options =>
{
    var conn = builder.Configuration.GetValue<string>("SqlServerUrl");
    options.UseSqlServer(conn);
});

appsettings.json文件内容: 

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "SqlServerUrl": "你的数据库连接字符串",
  "AllowedHosts": "*"
}

5. 在程序包管理器控制台输入
Add-Migration 此处自定义说明添加描述
举例: Add-Migration Init

Update-Database 更新到数据库

6.查询数据,插入数据

static void Main()
{
   
    using (MyDbContext ctx = new MyDbContext())
    {
        //向数据库插入数据
        //Book book = new Book();
        //book.Title = "标题2";
        //book.Price = 23.00;
        //book.AuthorName = "作者名字5";
        //book.PubTime = DateTime.Now;
        //ctx.books.Add(book); // 添加到Books逻辑表里面
        //ctx.SaveChanges(); 保存,同步到数据库

        //查询数据
        var items = ctx.books.Where(m => m.Price >= 50);
        foreach (var item in items)
        {
            Console.WriteLine(item.Price);
        }

        var s = ctx.books.OrderBy(m => m.Price);
        foreach (var item in s)
        {
            Console.WriteLine(item.Price);
        }
        Console.ReadKey();
    }
}

 6. 编辑数据,删除数据

//修改数据,删除数据
var b = ctx.books.Single(i => i.Id == 1);
b.Title = "新标题1";

var d = ctx.books.Single(n=>n.Id == 8);
ctx.books.Remove(d);

ctx.SaveChanges();