public interface IUnitOfWork : IDisposable
    {
        UserRepository Users { get; }
        int Complete();
    }

public interface IRepository <T> where T : class
{
    T Get(int id);
    IEnumerable<T> GetAll();
    IEnumerable<T> Find(Expression<Func<T,bool>> predicate);

    void Add(T entity);

    void Remove(T entity);
}

public class Repository<T> : IRepository<T> where T : class
{

    //Impelement all functions in IRepository (Actually Using EF Context functions
}

public class UserRepository : Repository<User>
{
    public UserRepository(NamaContext context) : base(context)
    {

    }
}

public class UserService
{

    public bool CheckLogin(User input)
    {
        using (var db = new UnitOfWork(new NamaContext()))
        {
            User dbUser = db.Users.GetByUserName(input.UserName);
            if (dbUser == null)
                return false;
            return input.Password == dbUser.Password;
        }
    }
    //other functions....
}