Error while validating the service descriptor 'ServiceType: INewsRepository Lifetime: Singleton ImplementationType: NewsRepository':

Question

I try get data from my database with repository Pattern i have 3 project

Bmu.Mode 'this is for model to create database'

Bmu.Repo 'it have 2 folder for repository include contract/InewsRepository.cs' and 'Repository/NewsRepository' for implement Interface

Bmu.Api for invoke data from Repo project

news class in Model Project

namespace bmu.model
{
   public class News
   {
    public int Id { get; set; }

    public string SubTitle { get; set; }

    public string Title { get; set; }

    public string Summery { get; set; }
  }
}

context class in model project

namespace bmu.model
 {
   public class BmuContext : DbContext
    {
       public BmuContext(DbContextOptions<BmuContext> options): base(options)
      {

      }
    public DbSet<News> News { get; set; }
   }
}

My interface in Repo project

namespace bmu.repo.Contracts
{
  public interface INewsRepository
  {
    Task<IEnumerable<News>> GetAllAsync();
    Task<IEnumerable<News>> GetAllActiveAsync();
  }
}

implement interface in bmu.repo

namespace bmu.repo.IRepository
{
 public class NewsRepository : INewsRepository
 {
    private readonly BmuContext _context;
    private readonly MemoryCache _memoryCache;

    public NewsRepository(BmuContext context, MemoryCache memoryCache)
    {
        _context = context;
        _memoryCache = memoryCache;
    }
    public async Task<IEnumerable<News>> GetAllAsync()
    {
        return await _context.News.ToListAsync(); 
    }
    public async Task<IEnumerable<News>> GetAllActiveAsync()
    {
      return   await _context.News.Where(x => x.Active).ToListAsync();
    }

}
}

Also add

services.AddControllers(); 
        services.AddSingleton<INewsRepository, NewsRepository>();

in startup of Api project and this is my controller

namespace bmu.api.Controllers
{
[ApiController]
[Route("[controller]")]
public class NewsController : ControllerBase
{
     private readonly ILogger<NewsController> _logger;
     private readonly INewsRepository _newsRepository;

    public NewsController(ILogger<NewsController> logger,INewsRepository newsRepository)
    {
        _logger = logger;
        _newsRepository = newsRepository; 
    }
    [HttpGet]
    public async Task<IEnumerable<News>> Get()
    {
        return await _newsRepository.GetAllActiveAsync();
    }
}
}

but when run project i got this error

AggregateException: Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: bmu.repo.Contracts.INewsRepository Lifetime: Singleton ImplementationType: bmu.repo.IRepository.NewsRepository': Unable to resolve service for type 'bmu.model.BmuContext' while attempting to activate 'bmu.repo.IRepository.NewsRepository'.)

also because of multi project add DbContext with this

UPDATE:

namespace bmu.model
{
public class BmuContextFactory : IDesignTimeDbContextFactory<BmuContext>
{
    public BmuContext CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<BmuContext>();
        optionsBuilder.UseSqlite("Data Source=bmu.db");

        return new BmuContext(optionsBuilder.Options);
    }
}
}

Is there any solution for this error ?

Answer 1

My Error was that I was injecting the service class instead of the interface

It was

  //This is wrong
Private readonly DataSerive _dataService;
public void EmployeeHandler(DataSerive dataService)
{
_dataService = dataService;
}

But it should be

 //This is correct
Private readonly IDataSerive _dataService;
public void EmployeeHandler(IDataSerive dataService)
{
_dataService = dataService;
}

Here DataService is the class that handles operation and IDataService is the interface