How to set small list of allowed dates in Calendar.

Environment

Product

Calendar for Blazor

Description

How to disable all dates that are not included in the AllowedDates collection (when the allowed dates are just a small list and all other dates should be disabled)?

Solution

1. Define a collection of dates that will contain the allowed dates.
2. Define a method that populates a collection of disabled dates based on the currently displayed dates by the View and the AllowedDates collection.
3. Define a ViewChanged Handler that will refresh the DisabledDates when the current View is changed.

<TelerikCalendar Date="@InitialDate"
                 Min="@MinDate"
                 Max="@MaxDate"
                 Views="@NumOfViews"
                 DisabledDates="@DisabledDates"
                 DateChanged="@DateChangedHandler"
                 SelectionMode="CalendarSelectionMode.Multiple" />

@code{
    private DateTime InitialDate { get; set; } = DateTime.Now;
    private DateTime MinDate { get; set; }
    private DateTime MaxDate { get; set; }
    private int NumOfViews { get; set; } = 3;

    private List<DateTime> AllowedDates = new List<DateTime>() { };

    // set dates the user can't select
    private List<DateTime> DisabledDates = new List<DateTime>() { };

    private void DateChangedHandler(DateTime firstDateOfNewRange)
    {
        DisableDates(firstDateOfNewRange);

        // if you don't do this, navigating adjacent ranges will be effectively disabled
        InitialDate = firstDateOfNewRange;
    }

    private void DisableDates(DateTime currentDate)
    {
        //Add the disabled dates we calculated into the DisabledDates parameter
        var disabledDates = GetDisabledDates(currentDate);
        DisabledDates = new List<DateTime>(disabledDates);
    }

    private IEnumerable<DateTime> GetDisabledDates(DateTime rangeStart)
    {
        //Start date of currently displayed month(s)
        var start = new DateTime(rangeStart.Year, rangeStart.Month, 1);
        //Compensate for the number of months displayed by the views number
        var end = start.AddMonths(NumOfViews).AddDays(-1);

        //Enumerate the number of days from the visible start-date till the end-date of the visible views
        //Except the dates available in AllowedDates
        var dateRange = Enumerable
            .Range(0, (int)(end - start).TotalDays + 1)
            .Select(i => start.AddDays(i))
            .Except(AllowedDates);

        return dateRange;
    }

    protected override void OnInitialized()
    {
        MinDate = new DateTime(InitialDate.AddYears(-5).Year, 1, 1);
        MaxDate = new DateTime(InitialDate.AddYears(5).Year, 12, 31);

        //Populate a list of allowed dates
        for (DateTime i = new DateTime(InitialDate.Year, 01, 01); i < new DateTime(InitialDate.AddYears(1).Year, 01, 01); i = i.AddDays(1))
        {
            if (i.Date.Day % 2 is 0)
                AllowedDates.Add(i);
        }

        //Call to fill initial dispaly page with disabled/allowed
        DisableDates(InitialDate);
    }
}