using Microsoft.AspNetCore.Mvc.Filters;

namespace IocCoreDemo
{
  public class ExceptionFilter : IExceptionFilter
  {
    private readonly LogService _logService;

    public ExceptionFilter(LogService logService)
    {
      _logService = logService;
    }

    public void OnException(ExceptionContext context)
    {
      _logService.Error(context.Exception.Message);
    }
  }
}

public class LogService
  {
    public void Error(string message)
    {
      Console.WriteLine(message);
    }
  }

public class Demo4Controller : Controller
  {
    public IActionResult Index()
    {
      throw new NotImplementedException();
    }
  }

public void ConfigureServices(IServiceCollection services)
    {
      services.AddSingleton(typeof(ExceptionFilter));   //注入 ExceptionFilter
      services.AddSingleton(typeof(LogService));     //注入 LogService

      services.AddMvc(x => {
        //创建一个 ServiceProvider 对象
        var provider = services.BuildServiceProvider();
        var filter = provider.GetService<ExceptionFilter>();

        //添加过滤器
        x.Filters.Add(filter);
      });
    }

public class Demo5Service
  {
    public string Test()
    {
      return Guid.NewGuid().ToString();
    }
}

public class Demo5Controller : Controller
  {
    public IActionResult Index()
    {
      var demoService = (Demo5Service) this.HttpContext.RequestServices.GetService(typeof(Demo5Service));
      return Json(demoService.Test());
    }
  }

public class Startup
  {
    public static ServiceProvider ServiceProvider { get; private set; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
      services.AddMvc();

      services.AddSingleton<Demo5Service>();

      ServiceProvider = services.BuildServiceProvider();
    }

    //...
  }

public class Demo5Controller : Controller
 {
  public IActionResult Index()
  {
   var demoService = (Demo5Service)Startup.ServiceProvider.GetService(typeof(Demo5Service));
   return Json(demoService.Test());
  }
 }