Not work function in generic class

public MainWindow()
  {
      var usersManagerService = StructureMapDefnation.Container.GetInstance<IUser>();

      var qUser = usersManagerService.Find(x => x.Username == "k" && x.Password == "k");
      InitializeComponent();

  }

public class EfUserService : EfGenericService<User>, IUser
    {
        public EfUserService(IUnitOfWork uow) : base(uow)
        {
        }
    }

public class EfGenericService<T> : IGenericService<T> where T : class
    {
        protected IUnitOfWork Uow;
        protected IDbSet<T> Entites;

        public EfGenericService(IUnitOfWork uow)
        {
            Uow = uow;
            Entites = Uow.Set<T>();
        }
         public T Find(Func<T, bool> predicate)
        {
            return Entites.Where(predicate).FirstOrDefault();
        }
    }

public T Find(Func<T, bool> predicate)
      {
          return Entites.Where(predicate).FirstOrDefault();
      }