Question

从控制器调用方法会产生错误InvalidOperationException：尝试激活“ AwardManagement.Controllers.TabsController”时，无法解析类型为“ AwardManagement.Class.Season”的服务。

这是控制器发出的代码


   public TabsController(AwardContext context,Season seasons)
   {
       _context = context;
       _seasons = seasons;
   }
   public ActionResult GetTabs(int id)
   {
       var tabs =  _context.Tabs.Find(id);
       if (tabs == null)
       {
          return NotFound();
       }
       var season = _seasons.GetSingle(tabs.SeasonId);
       var result = new { tab = tabs, season = season };
       return  Ok(result);
   }

季节类中的GetSingle（）定义

public class Season
{
     private readonly AwardContext _context;
     public Season(AwardContext context)
     {
        _context = context;
     } 
     public  Seasons GetSingle(int? id)
     {
        return _context.Seasons.FirstOrDefault(x => x.Id == id);
     }
 }

Answer 1

问题是您没有在DI容器中注册Season类，因此在该控制器中收到请求时，没人知道如何实例化TabsController，因为它不知道在何处获取Season参数。

您可以在此处了解更多信息：https://aspnetcore.readthedocs.io/en/stable/mvc/controllers/dependency-injection.html

除此以外，还有两种方法可以解决此问题：

将GetTab更改为直接使用_context.Seasons

   public TabsController(AwardContext context)
   {
       _context = context;
   }
   public ActionResult GetTabs(int id)
   {
       var tabs =  _context.Tabs.Find(id);
       if (tabs == null)
       {
          return NotFound();
       }
       var season = _context.Seasons.FirstOrDefault(tabs.SeasonId);
       var result = new { tab = tabs, season = season };
       return  Ok(result);
   }

或者您将逻辑移到一个单独的类（如服务）中：SeasonService，然后将其注册到DI容器中，然后在TabsController和{ SeasonController。

SeasonService将如下所示：

public class SeasonService
{
     private readonly AwardContext _context;
     public SeasonService(AwardContext context)
     {
        _context = context;
     } 
     public  Seasons GetSingle(int? id)
     {
        return _context.Seasons.FirstOrDefault(x => x.Id == id);
     }
 }

您需要在DI容器中注册它：https://medium.com/volosoft/asp-net-core-dependency-injection-best-practices-tips-tricks-c6e9c67f9d96

然后您就可以在控制器中使用它了：

   public TabsController(TabsService tabsService, SeasonService seasonService)
   {
       _tabsService = tabsService;
       _seasonService = seasonService;
   }
   public ActionResult GetTabs(int id)
   {
       var tabs =  _tabsService.FindById(id);
       if (tabs == null)
       {
          return NotFound();
       }
       var season = _seasonService.GetSingleById(tabs.SeasonId);
       var result = new { tab = tabs, season = season };
       return  Ok(result);
   }

如您所见，您还需要创建TabsService并在DI容器中注册它。

您可以在此处了解有关这种设计模式/建筑方法的更多信息：MVCS - Model View Controller Service

Answer 2

要获得明确的解决方案，请像{p>一样在Season中注册Startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {            
        services.AddScoped<Season>();           
    }
}

当另一个类的控制器调用方法产生无效操作时

2 个答案: