[.Net] .NET学习笔记之默认依赖注入

　　只要是用new实例化的都是存在依赖的。

services.AddSingleton<IApplicationService,ApplicationService>

services.AddScoped<IApplicationService,ApplicationService>

services.AddTransient<IApplicationService,ApplicationService>

/// <summary>
  /// 用户接口
  /// </summary>
  public interface IUserService
  {
    string GetName();
  }
  /// <summary>
  /// 用户实现
  /// </summary>
  public class UserService : IUserService
  {
    public string GetName()
    {
      return "AZRNG";
    }
  }

private readonly IUserService _userService;
    public UserController(IUserService userService)
    {
      _userService = userService;
    }
    [HttpGet]
    public ActionResult GetName()
    {
      return Ok(_userService.GetName());
    }
FromServices操作注入
    [HttpGet]
    public ActionResult GetName([FromServices] IUserService _userService)
    {
      return Ok(_userService.GetName());
    }

   

• IServiceCollection负责注册   
  
• IServiceProvider负责提供实例
  

public void ConfigureServices(IServiceCollection services)
{
  //将服务生命期的范围限定为单个请求的生命期
  services.AddTransient<IUserService, UserService>();
}

private readonly IUserService _userService;
    public HomeController(IUserService userService)
    {
      _userService = userService;
    }
    public IActionResult Index()
    {
      var info = _userService.GetInfo();
      return View();
    }

private readonly IServiceProvider _service;
    public UserController(IServiceProvider service)
    {
      _service = service;
    }
    [HttpGet]
    public ActionResult GetName()
    {
      var _userService = (IUserService)_service.GetService(typeof(IUserService));
      return Ok(_userService.GetName());
    }

var provider = services.BuildServiceProvider();
var userserivce = provider.GetService<IUserService>();
//或
var userservice2 = provider.GetRequiredService<IUserService>();