Collections and dates

Collections

using HeroKit.Enumerables;

items.IsNullOrEmpty();                               // null-safe; reads at most one element of a lazy sequence
products.WhereIf(onlyInStock, p => p.Stock > 0);     // filter only when the condition is true
query.OrderBy(x => x.Id).Page(pageNumber: 2, pageSize: 20); // 1-based paging
source.ToReadOnlyList();                             // read-only copy

WhereIf and Page also work on IQueryable<T>, so Entity Framework translates them to SQL.

Dates

using HeroKit.DateTimes;

var date = new DateTime(2024, 2, 15, 13, 45, 0);

date.StartOfMonth();     // 2024-02-01 00:00:00
date.EndOfMonth();       // 2024-02-29 23:59:59.9999999
date.StartOfWeek();      // Monday 2024-02-12
date.IsWeekend();        // false
new DateTime(1990, 2, 15).Age(asOf: date); // 34

date.AsFileName("Monthly Report"); // "monthly-report-2024-02-15-13-45-00"

Business days

Business days and public holidays take a Country with a holiday calendar:

using HeroKit.Globalization;

var day = new DateOnly(2026, 3, 19);

day.IsBusinessDay(Countries.Turkey);               // true
day.AddBusinessDays(1, Countries.Turkey);          // 2026-03-23, skips the bayram and the weekend
day.BusinessDaysUntil(new DateOnly(2026, 3, 27), Countries.Turkey); // business days after day, up to and including 27 March
new DateOnly(2026, 10, 29).IsPublicHoliday(Countries.Turkey); // true

See Countries and languages for holidays, half days and how to add a calendar for another country.

Results keep the DateTimeKind of the input. DateOnly overloads are available for week, month, weekend, range and age helpers.