Invalidoperationexception: Unable to resolve service for type while attempting to Activate

Question

This is probably a duplicate question, but all the questions I saw didn’t solve the problem.

The mistake happening is:

The flow is as follows: View -> Controller -> Service -> Repository

Dependency Injection is not working for the service applied to Scoped in the file Statup.Cs.

public void ConfigureServices(IServiceCollection services)
    {

        var connection = Configuration["SqlConnection:SqlConnectionString"];
        services.AddDbContext<AimbraDocContext>(options => options.UseSqlServer(connection));

        services.Configure<CookiePolicyOptions>(options =>
        {
            options.CheckConsentNeeded = context => true;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddScoped<IUserService, UserServiceImpl>();
        services.AddScoped<IUserRepository, UserRepositoryImpl>();
        services.AddScoped(
            typeof(IRepository<>),
            typeof(GenericRepository<>)
            );


        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

The problem is happening with Userservice, where I have the following interface and implementation:

public interface IUserService
    {
        UserVM Create(UserVM user);

        List<UserVM> FindAll();

        UserVM FindbyUsername(string username);

        UserVM FindbyEmail(string email);

        UserVM FindById(int id);

        UserVM Update(UserVM user);

        void Delete(int id);
    }

public class UserServiceImpl : IUserService
    {

        private readonly UserConverter _converter;
        private readonly IUserRepository _repository;

        public UserServiceImpl(UserConverter converter, IUserRepository repository)
        {
            _repository = repository;
            _converter = new UserConverter();
        }

        public UserVM Create(UserVM user)
        {
            var userEntity = _converter.Parse(user);
            userEntity.CreatedAt = new DateTime();
            userEntity.UpdatedAt = new DateTime();
            userEntity.Token = Guid.NewGuid().ToString("N").Substring(0, 5);
            userEntity.TokenCreatedAt = new DateTime();

            userEntity = _repository.Create(userEntity);

            return _converter.Parse(userEntity);
        }

        public void Delete(int id)
        {
            _repository.Delete(id);
        }

        public List<UserVM> FindAll()
        {
            return _converter.ParseList(_repository.FindAll());
        }

        public UserVM FindbyEmail(string email)
        {
            return _converter.Parse(_repository.FindByEmail(email));
        }

        public UserVM FindById(int id)
        {
            return _converter.Parse(_repository.FindById(id));
        }

        public UserVM FindbyUsername(string username)
        {
            return _converter.Parse(_repository.FindByUsername(username));
        }

        public UserVM Update(UserVM user)
        {
            var userEntity = _converter.Parse(user);
            userEntity.UpdatedAt = new DateTime();
            userEntity = _repository.Update(userEntity);
            return _converter.Parse(userEntity);
        }
    }

My View:

@model AimbraDocMVC.Data.VM.UserVM

@{
    ViewData["Title"] = "Index";
}

<h2>Index</h2>

<h4>UserVM</h4>
<hr />
<div class="row">
    <div class="col-md-4">
        <form asp-action="Index">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="Username" class="control-label"></label>
                <input asp-for="Username" class="form-control" />
                <span asp-validation-for="Username" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Password" class="control-label"></label>
                <input asp-for="Password" class="form-control" />
                <span asp-validation-for="Password" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="PasswordConfirm" class="control-label"></label>
                <input asp-for="PasswordConfirm" class="form-control" />
                <span asp-validation-for="PasswordConfirm" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Email" class="control-label"></label>
                <input asp-for="Email" class="form-control" />
                <span asp-validation-for="Email" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </form>
    </div>
</div>

<div>
    <a asp-action="Index">Back to List</a>
</div>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

The implementation of the Userrepository:

public class UserRepositoryImpl : GenericRepository<User>, IUserRepository
    {   
        public UserRepositoryImpl(AimbraDocContext context) : base(context)
        {
        }

        public User FindByEmail(string email)
        {
            if (email == null) return null;
            var result  = _context.Users.SingleOrDefault(u => u.Email.Equals(email));
            if (result == null) return null;
            return result;
        }

        public User FindByUsername(string username)
        {
            if (username == null) return null;
            var result = _context.Users.SingleOrDefault(u => u.Username.Equals(username));
            if (result == null) return null;
            return result;
        }
    }