public void Update(BudgetViewModel budget)
        {
            var entity = _repository.Get(budget.YearMonth);

            entity.Amount = budget.Amount;
            _repository.Save(entity);
        }
 public void Add(BudgetViewModel budget)
 {
     _repository.Save(new BudgetEntity()
     {
         Id     = budget.YearMonth,
         Amount = budget.Amount
     });
 }