214 lines
9.7 KiB
C#
214 lines
9.7 KiB
C#
using Elternbeirat.Contracts;
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using Elternbeirat.Web.Shared;
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namespace Elternbeirat.Web.Features.Events;
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/// <summary>
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/// Formats the date range of an <see cref="Event"/> for display in German.
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/// </summary>
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/// <remarks>
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/// Shared by the full event list, the home-page events embed and the next-event
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/// card, so all render dates the same way: <see cref="Range"/> as the full date,
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/// the <c>Sheet…</c> methods and <see cref="Span"/> for the calendar sheet and the
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/// time line beside it, <see cref="PastDays"/> and <see cref="PastTime"/> for the list of past events.
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/// <para>
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/// This is the event counterpart to
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/// <see cref="Posts.PostDateFormat"/>, which formats a plain
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/// <see cref="DateOnly"/> day instead of a point-in-time range.
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/// </para>
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/// </remarks>
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public static class EventDateFormat
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{
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/// <summary>
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/// Date format for the start, and for a single-day event.
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/// </summary>
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private const string LongDate = "dddd, d. MMMM yyyy";
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/// <summary>
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/// Date format for the end of a multi-day event; the weekday is omitted.
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/// </summary>
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private const string ShortDate = "d. MMMM yyyy";
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/// <summary>
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/// Date format for the list of past events, which is grouped by year.
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/// </summary>
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private const string DayMonth = "d. MMMM";
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/// <summary>
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/// Formats the date range of an event.
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/// </summary>
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/// <param name="event">
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/// The event to format.
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/// </param>
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/// <returns>
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/// The formatted range, depending on <see cref="Event.End"/> and <see cref="Event.HasTime"/>:
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/// <list type="bullet">
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/// <item>
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/// <description>No end: <c>Donnerstag, 8. Oktober 2026, 19:30 Uhr</c></description>
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/// </item>
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/// <item>
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/// <description>Same day: <c>Donnerstag, 8. Oktober 2026, 19:30–21:00 Uhr</c></description>
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/// </item>
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/// <item>
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/// <description>Several days: <c>Freitag, 9. Oktober 2026 – 11. Oktober 2026</c></description>
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/// </item>
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/// </list>
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/// Without a time, the time parts are omitted.
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/// </returns>
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public static string Range(Event @event)
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=> (@event.Start, @event.End, @event.HasTime) switch
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{
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(var start, null, var hasTime)
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=> Stamp(start, LongDate, hasTime),
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(var start, { } end, true) when end.Date == start.Date
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=> $"{start.ToString(LongDate, Cultures.German)}, {Clock(start)}–{Clock(end)} Uhr",
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(var start, { } end, false) when end.Date == start.Date
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=> Stamp(start, LongDate, withTime: false),
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(var start, { } end, var hasTime)
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=> $"{Stamp(start, LongDate, hasTime)} – {Stamp(end, ShortDate, hasTime)}",
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};
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/// <summary>
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/// The short month for the top band of a calendar sheet.
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/// </summary>
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/// <param name="value">The event's start.</param>
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/// <returns>The German short month without its period, e.g. <c>Okt</c> or <c>März</c>.</returns>
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/// <remarks>
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/// Returned in normal case; the sheet's CSS sets it in capitals. The period of the
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/// abbreviation (<c>Okt.</c>) is dropped because on a sheet it reads as a stray dot.
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/// </remarks>
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/// <seealso cref="CalendarSheet"/>
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public static string SheetMonth(DateTime value)
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=> value.ToString("MMM", Cultures.German).TrimEnd('.');
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/// <summary>
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/// The day of the month for the large number on a calendar sheet.
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/// </summary>
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/// <param name="value">The event's start.</param>
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/// <returns>The day without a leading zero, e.g. <c>8</c>.</returns>
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public static string SheetDay(DateTime value)
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=> value.Day.ToString(Cultures.German);
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/// <summary>
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/// The short weekday for the bottom of a calendar sheet.
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/// </summary>
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/// <param name="value">The event's start.</param>
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/// <returns>The German short weekday without its period, e.g. <c>Do</c>.</returns>
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public static string SheetWeekday(DateTime value)
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=> value.ToString("ddd", Cultures.German).TrimEnd('.');
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/// <summary>
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/// The time line beside a calendar sheet: what the sheet itself cannot show.
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/// </summary>
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/// <param name="event">The event to format.</param>
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/// <returns>
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/// Depending on <see cref="Event.End"/> and <see cref="Event.HasTime"/>:
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/// <list type="bullet">
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/// <item><description>No end: <c>19:30 Uhr</c></description></item>
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/// <item><description>Same day: <c>19:30–21:00 Uhr</c></description></item>
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/// <item><description>Several days: <c>09:00 Uhr bis Sonntag, 11. Oktober 2026, 13:00 Uhr</c></description></item>
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/// <item><description>Several days, no time: <c>bis Sonntag, 11. Oktober 2026</c></description></item>
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/// <item><description>One day, no time: an empty string; the sheet says it all.</description></item>
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/// </list>
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/// </returns>
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/// <remarks>
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/// The sheet shows the start day only, so a multi-day event must name its last
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/// day here, with the weekday, as the sheet does for the first one.
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/// </remarks>
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public static string Span(Event @event)
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=> (@event.Start, @event.End, @event.HasTime) switch
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{
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(var start, { } end, var hasTime) when end.Date != start.Date
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=> (hasTime ? Clock(start) + " Uhr " : "") + "bis " + Stamp(end, LongDate, hasTime),
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(var start, null, true)
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=> $"{Clock(start)} Uhr",
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(var start, { } end, true)
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=> $"{Clock(start)}–{Clock(end)} Uhr",
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_ => "",
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};
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/// <summary>
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/// The day column of a past event in the folded-up list on the events page.
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/// </summary>
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/// <param name="event">The event to format.</param>
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/// <returns>
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/// Day and full month, depending on <see cref="Event.End"/>:
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/// <list type="bullet">
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/// <item><description>One day: <c>13. November</c></description></item>
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/// <item><description>Several days in one month: <c>8.–9. Februar</c></description></item>
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/// <item><description>Across a month: <c>30. Januar – 2. Februar</c></description></item>
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/// <item><description>Across a year: <c>30. Dezember – 2. Januar 2027</c></description></item>
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/// </list>
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/// </returns>
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/// <remarks>
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/// The list is grouped by the start year under its own small heading, so the
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/// year is only named where the end leaves that year. The weekday is left out
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/// to keep the column short; the time follows the title (<see cref="PastTime"/>).
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/// </remarks>
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public static string PastDays(Event @event)
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=> (@event.Start, @event.End) switch
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{
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(var start, { } end) when end.Year != start.Year
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=> $"{start.ToString(DayMonth, Cultures.German)} – {end.ToString(ShortDate, Cultures.German)}",
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(var start, { } end) when end.Month != start.Month
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=> $"{start.ToString(DayMonth, Cultures.German)} – {end.ToString(DayMonth, Cultures.German)}",
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(var start, { } end) when end.Day != start.Day
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=> $"{start.Day.ToString(Cultures.German)}.–{end.ToString(DayMonth, Cultures.German)}",
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(var start, _)
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=> start.ToString(DayMonth, Cultures.German),
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};
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/// <summary>
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/// The time after the title of a past event in the folded-up list.
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/// </summary>
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/// <param name="event">The event to format.</param>
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/// <returns>
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/// Depending on <see cref="Event.HasTime"/> and <see cref="Event.End"/>:
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/// <list type="bullet">
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/// <item><description>No time: an empty string; nothing is shown.</description></item>
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/// <item><description>No end: <c>19:00 Uhr</c></description></item>
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/// <item><description>Same day: <c>19:00–21:00 Uhr</c></description></item>
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/// <item><description>Several days: the start time only, <c>09:00 Uhr</c></description></item>
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/// </list>
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/// </returns>
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/// <remarks>
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/// For several days the day column already shows the span; a time range beside
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/// it would read as the daily hours, so only the start time is given.
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/// </remarks>
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public static string PastTime(Event @event)
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=> (@event.HasTime, @event.End) switch
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{
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(false, _) => "",
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(true, { } end) when end.Date != @event.Start.Date => $"{Clock(@event.Start)} Uhr",
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_ => Span(@event),
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};
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/// <summary>
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/// Formats the clock time of a point in time.
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/// </summary>
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/// <param name="value">The date and time.</param>
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/// <returns>The time as e.g. <c>19:30</c>.</returns>
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private static string Clock(DateTime value)
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=> value.ToString("HH:mm", Cultures.German);
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/// <summary>
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/// Formats a single point in time as a date with an optional time.
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/// </summary>
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/// <param name="value">
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/// The date and time to format.
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/// </param>
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/// <param name="dateFormat">
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/// The date format, e.g. <see cref="LongDate"/>.
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/// </param>
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/// <param name="withTime">
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/// <see langword="true"/> to append the time, e.g. <c>, 19:30 Uhr</c>.
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/// </param>
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/// <returns>
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/// The formatted date, with the time if requested.
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/// </returns>
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private static string Stamp(DateTime value, string dateFormat, bool withTime)
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=> withTime
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? value.ToString(dateFormat + ", HH:mm", Cultures.German) + " Uhr"
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: value.ToString(dateFormat, Cultures.German);
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}
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