public async Task OnGet()
        {
            // set start and end dates as this month
            DateTime today = DateTime.Now;

            Query = new GetShiftRosterQuery
            {
                StartDate = new DateTime(today.Year, today.Month, 1)
            };
            Query.EndDate = Query.StartDate.AddMonths(1).AddDays(-1);
            // get roster data
            Roster = await _mediator.Send(Query);
        }
        public async Task <IActionResult> OnPostAsync()
        {
            var validator        = new GetShiftRosterQueryValidator();
            var validationResult = validator.Validate(Query);

            if (!validationResult.IsValid)
            {
                validationResult.AddToModelState(ModelState, null);
                return(Page());
            }
            // get roster data
            Roster = await _mediator.Send(Query);

            return(Page());
        }