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 ?

Solution 1

It was because of

    private readonly IMemoryCache _memoryCache;

when i remove it every think work fine

Solution 2

Firstly,you need to change:

services.AddSingleton<INewsRepository, NewsRepository>();

To:

services.AddTransient<INewsRepository, NewsRepository>();

Secondly,you need to inject IMemoryCache instead of MemoryCache in NewsRepository.

Here is a simple demo like below:

1.Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllersWithViews();
    services.AddSession();
    services.AddTransient<INewsRepository, NewsRepository>();
    services.AddDbContext<BmuContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("Connectionstring")));
    services.AddMemoryCache();
}

2.appsettings.json:

"ConnectionStrings": {
    "Connectionstring": "Server=(localdb)\\mssqllocaldb;Database=Bmu;Trusted_Connection=True;MultipleActiveResultSets=true"  
}

3.NewsRepository:

public class NewsRepository : INewsRepository
{
    private readonly BmuContext _context;
    private readonly IMemoryCache _memoryCache;

    public NewsRepository(BmuContext context, IMemoryCache memoryCache)
    {
        _context = context;
    }
    //...
}

Solution 3

There is a lifetime type mismatch in your API. EntityFramework DbContext is a scoped service, and you cannot have a singleton instance of the NewsRepository, as it depends on an instance that is generated for each request.

You either have to use NewsRepository as a scoped service, or restructure your dependency resolution, like shown in this SO answer: Use DbContext in ASP .Net Singleton Injected Class

Solution 4

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

Solution 5

Like Sotiris Koukios-Panopoulos -san comment

I see you are only setting up the options for design time, not in your Startup.cs. I expect a:

services.AddDbContext<BmuContext>(options => options.UseSqlite("your connection string"));

instead.

In my case, I forgot to set this in my Startup.cs

services.AddDbContext<myDbContext>(o => o.UseSqlServer(myConnectionString));

and I forgot to mention this, because I'm using interface an service

services.AddScoped<IMyTruckService, MyTruckService>();

View more solutions

Comments

[sunny]

I use services.AddScoped<INewsRepository, NewsRepository>();but get this error again

[Sotiris Koukios-Panopoulos]

How are you registering your BmuContext?

[sunny]

services.AddDbContext<BmuContext>(); Also update my question

[Sotiris Koukios-Panopoulos]

I see you are only setting up the options for designtime, not in your Startup.cs. I expect a services.AddDbContext<BmuContext>(options => options.UseSqlite(your connection string)); instead

[sunny]

I do All of think, remove " private readonly IMemoryCache _memoryCache;" from Repository and avery think work fine

[Rena]

If my answer is helpful,could you accept as answer?

[Amin Golmahalle]

Your answer is not logical.

[sunny]

I think its because of don't register IMemoryCache in startup.cs in service, it logical

[Karim Alaa]

Is IMemoryCache was registerd in startup.cs?

[Guy Levy]

Welcome to SO. its not clear if your post is answering the original question. If you believe your post answers it, please elaborate why and how with more detail

[malik masis]

Also, you should sign Rena's answer as an accepted answer

[Léon Pelletier]

I'd also add to @malik comment: You should sign Rena's answer as an accepted answer.

[UC57]

In my case, i created non-public constructor. Resolved by creating it public and it works.