EFcore 依赖注入

基于EFcore 采用DBFirst模式 实现DBContext依赖注入

1.SQL Server创建数据库

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：

2.VS引入Nuget程序包

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

3.Scaffold-DbContext框架生成Model

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<ExampleContext> options): base(options){
    }public virtual DbSet<Contact> Contacts {
     get; set; }public virtual DbSet<UserInfo> UserInfos {
     get; set; }protected override void OnModelCreating(ModelBuilder modelBuilder){
    modelBuilder.HasAnnotation("Relational:Collation", "Chinese_PRC_CI_AS");modelBuilder.Entity<Contact>(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<UserInfo>(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);}
}

4.依赖注入DBContext

Startup类中依赖注入

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllersWithViews();services.AddDbContext<ExampleContext>(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.

5.DBContext构造函数注入

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<HomeController> _logger;private readonly ExampleContext _db;public HomeController(ILogger<HomeController> logger,ExampleContext exampleContext){
    _logger = logger;_db = exampleContext;}public IActionResult Index(){
    var query = _db.UserInfos.Find(1);return View();}      }
}