.NET CORE 2.0 Unable to resolve service for type while attempting to activate

Question

I have a IDataRepository.cs file that contains an interface and its implementation like so:

public interface IDataRepository<TEntity, U> where TEntity : class
{
    IEnumerable<TEntity> GetAll();
    TEntity Get(U id);
    TEntity GetByString(string stringValue);
    long Add(TEntity b);
    long Update(U id, TEntity b);
    long Delete(U id);
}

I have another class TokenManager.cs that implements IDataRepository Interface:

public class TokenManager : IDataRepository<Token, long>
{
    ApplicationContext ctx;
    public TokenManager(ApplicationContext c)
    {
        ctx = c;
    }

    //Get the Token Information by ID
    public Token Get(long id)
    {
        var token = ctx.Token.FirstOrDefault(b => b.TokenId == id);
        return token;
    }

    public IEnumerable<Token> GetAll()
    {
        var token = ctx.Token.ToList();
        return token;
    }


    //Get the Token Information by ID
    public Token GetByString(string clientType)
    {
        var token = ctx.Token.FirstOrDefault(b => b.TokenClientType == clientType);
        return token;
    }

    public long Add(Token token)
    {
        ctx.Token.Add(token);
        long tokenID = ctx.SaveChanges();
        return tokenID;
    }

}

and finally, I have a controller to put all things together, my controller files looks like this:

[Route("api/[controller]")]
public class TokenController : Controller
{
    private IDataRepository<Token, long> _iRepo;
    public TokenController(IDataRepository<Token, long> repo)
    {
        _iRepo = repo;
    }

    // GET: api/values  
    [HttpGet]
    public IEnumerable<Token> Get()
    {
        return _iRepo.GetAll();
    }

    // GET api/values/produccion
    [HttpGet("{stringValue}")]
    public Token Get(string stringValue)
    {
        return _iRepo.GetByString(stringValue);
    }
}

But the problem is that every time I try to access some method from my API, for example using postman I get the error:

InvalidOperationException: Unable to resolve service for type FECR_API.Models.Repository.IDataRepository`2[FECR_API.Models.Token,System.Int64] while attempting to activate;FECR_API.Controllers.TokenController

I tried using something like this inside ConfigureServices, but get a conversion error

services.AddScoped<IDataRepository, TokenManager>();

Any idea what I'm doing wrong?

Solution

Please ensure you register dependencies in DI container inside Startup.cs

public class Startup
{  
    ...

    public void ConfigureServices(IServiceCollection services)
    {
        ...
        services.AddScoped<IDataRepository<Token, long>, TokenManager>();
        ...
    }
}