When controller call method from another class produce produce invalid operation

Question

Calling a method from controller produce the error InvalidOperationException: Unable to resolve service for type 'AwardManagement.Class.Season' while attempting to activate 'AwardManagement.Controllers.TabsController'.

This is the code call from Controller

   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);
   }

GetSingle() Definition in Season Class

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

The problem is that you didn't registered your Season class in the DI container so when a request is received in that controller no one knows how to instantiate TabsController because it doesn't know from where to get the Season parameter.

You can read more here: https://aspnetcore.readthedocs.io/en/stable/mvc/controllers/dependency-injection.html

Apart from this there are two ways to resolve this one:

1. Change the GetTabs to directly use _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);
      }
   

2. Or you move the logic into a separate class (like a service): SeasonService, then you register that in the DI container, then you re-use it in both TabsController and SeasonController.

The SeasonService will look something like this:

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);
     }
 }

And you need to register it in DI container: https://medium.com/volosoft/asp-net-core-dependency-injection-best-practices-tips-tricks-c6e9c67f9d96

And then you'll be able to use it inside your controllers:

   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);
   }

As you can see, you'll need to also create TabsService and register it too in DI Container.

You can read more about this design pattern/architectural approach here: MVCS - Model View Controller Service

Answer 2

For a clear solution, register Season in the Startup.cs like

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>();           
    }
}