public void ExecuteDellCurrentSleepTimeCommand(object parametr) { NewSleep.Time = DateTime.Now; TotalSleepTime = TotalSleepTime.Subtract(TimeSpan.FromSeconds(CurrentSleep.GetDurationInSecond())); SleepRepository.Instance.DeleteOperation(CurrentSleep); DaySleepTime.Remove(CurrentSleep); OnPropertyChanged("TotalSleepTime"); CommandManager.InvalidateRequerySuggested(); if (DaySleepTime.Count > 0) { CurrentSleep = DaySleepTime.First(); } CheckTotalSleepTime(); }