public void AddHoliday()
 {
     MainScreenViewModel.ShowPopup(AddHolidayViewModel.CreateForAdd(MainScreenViewModel, new AddHolidayViewModel.AddParameter()
     {
         SemesterIdentifier = MainScreenViewModel.CurrentSemesterId,
         StartDate          = CurrentDate,
         EndDate            = CurrentDate
     }));
 }
        private void AddHoliday()
        {
            var viewModel = PowerPlannerApp.Current.GetMainScreenViewModel();

            if (viewModel != null)
            {
                viewModel.ShowPopup(AddHolidayViewModel.CreateForAdd(viewModel, new AddHolidayViewModel.AddParameter()
                {
                    SemesterIdentifier = viewModel.CurrentSemester.Identifier,
                    StartDate          = DateToUseForNewItems != null ? DateToUseForNewItems.Value : DateTime.Today,
                    EndDate            = DateToUseForNewItems != null ? DateToUseForNewItems.Value : DateTime.Today
                }));
            }
        }
        private void AddHolidayHelper(DateTime?date = null, bool useSelectedDate = true)
        {
            date = GetDateForAdd(date, useSelectedDate);
            if (date == null)
            {
                date = DateTime.Today;
            }

            MainScreenViewModel.ShowPopup(AddHolidayViewModel.CreateForAdd(MainScreenViewModel, new AddHolidayViewModel.AddParameter()
            {
                SemesterIdentifier = MainScreenViewModel.CurrentSemesterId,
                StartDate          = date.Value,
                EndDate            = date.Value
            }));
        }