EFcore 依赖注入

创建一个名为Example的数据库，并含有UserInfo、Contacts数据表

UserInfo字段：

Contacts字段：

可以在程序包管理控制台 手动键入命令行安装Nuget包:

install-package microsoft.entityframeworkcore
install-package microsoft.entityframeworkcore.sqlserver
install-package mircosoft.entityframeworkcore.tools

Scaffold-DBContext “server=.;database=Example;uid=sa;pwd=sa123456” microsoft.entityframeworkcore.sqlserver -outputDir Models

命令行说明：

框架Build Succeed后，自动生成数据库实体类与DbContext类

UserInfo：

namespace WebApplication24.Models
{
    public partial class UserInfo
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int? Age { get; set; }
    }
}

Contact：

namespace WebApplication24.Models
{
    public partial class Contact
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Phone { get; set; }
        public string Address { get; set; }
    }
}

ExampleContext：

namespace WebApplication24.Models
{
    public partial class ExampleContext : DbContext
    {
        public ExampleContext()
        {
        }

        public ExampleContext(DbContextOptions options)
            : base(options)
        {
        }

        public virtual DbSet Contacts { get; set; }
        public virtual DbSet UserInfos { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.HasAnnotation("Relational:Collation", "Chinese_PRC_CI_AS");

            modelBuilder.Entity(entity =>
            {
                entity.Property(e => e.Id)
                    .ValueGeneratedNever()
                    .HasColumnName("ID");

                entity.Property(e => e.Address).HasMaxLength(50);

                entity.Property(e => e.Name).HasMaxLength(50);

                entity.Property(e => e.Phone).HasMaxLength(50);
            });

            modelBuilder.Entity(entity =>
            {
                entity.ToTable("UserInfo");

                entity.Property(e => e.Id)
                    .ValueGeneratedNever()
                    .HasColumnName("ID");

                entity.Property(e => e.Name).HasMaxLength(50);
            });

            OnModelCreatingPartial(modelBuilder);
        }
        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }
}

Startup类中依赖注入

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllersWithViews();

    services.AddDbContext(options => {
        options.UseSqlServer(Configuration.GetConnectionString("defaultConnection"));
    });
}

appsettings.json中加入连接字符串

"ConnectionStrings": {
    "defaultConnection": "server=.;database=example;uid=sa;pwd=sa123456"
  }

AddDbContext解释摘要：

摘要:
        //     Registers the given context as a service in the Microsoft.Extensions.DependencyInjection.IServiceCollection.
        //     Use this method when using dependency injection in your application, such as
        //     with ASP.NET Core. For applications that don't use dependency injection, consider
        //     creating Microsoft.EntityFrameworkCore.DbContext instances directly with its
        //     constructor. The Microsoft.EntityFrameworkCore.DbContext.OnConfiguring(Microsoft.EntityFrameworkCore.DbContextOptionsBuilder)
        //     method can then be overridden to configure a connection string and other options.
        //     For more information on how to use this method, see the Entity Framework Core
        //     documentation at https://aka.ms/efdocs. For more information on using dependency
        //     injection, see https://go.microsoft.com/fwlink/?LinkId=526890.

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using WebApplication24.Models;

namespace WebApplication24.Controllers
{
    public class HomeController : Controller
    {
        private readonly ILogger _logger;
        private readonly ExampleContext _db;

        public HomeController(ILogger logger,ExampleContext exampleContext)
        {
            _logger = logger;
            _db = exampleContext;
        }

        public IActionResult Index()
        {
            var query = _db.UserInfos.Find(1);
            return View();
        }      
    }
}