public async void ChangedDatesAsync()
{
DateStart = DateFinish.Subtract(new TimeSpan(30, 0, 0, 0));
Incomes = await repository.GetIncomeAsync(DateStart, DateFinish);
Costs = await repository.GetCostsAsync(DateStart, DateFinish);
AccountRepository accRepository = new AccountRepository(User);
float totalActivies = await accRepository.GetTotalActiviesAsync();
Yield = Incomes / Costs;
Welfare = totalActivies / Costs;
}