توابع استفاده از تاریخ شمسی در #C

using System.Globalization;

 public static string PersianDate(System.DateTime TodayDate)
 {
     string Per;
     PersianCalendar ps = new();
     Per = ps.GetYear(TodayDate) + "/" + ps.GetMonth(TodayDate).ToString("00") + "/" + ps.GetDayOfMonth(TodayDate).ToString("00");
     return Per;
 }

 public static string RoozPersian(DateTime TodayDate)
 {

     return $"امروز {GetDayOfWeek(TodayDate)} ، {PersianDate(TodayDate).Substring(8, 2)} {DateMahFarsi(PersianDate(TodayDate).Substring(5, 2))} سال {PersianDate(TodayDate).Substring(0, 4)}";
 }

public static string GetDayOfWeek(System.DateTime DateString)
{
    PersianCalendar Pt = new PersianCalendar();
    DayOfWeek day = Pt.GetDayOfWeek(DateString);
    switch (day)
    {
        case DayOfWeek.Saturday:
            return "شنبه";
        case DayOfWeek.Sunday:
            return "یکشنبه";
        case DayOfWeek.Monday:
            return "دوشنبه";
        case DayOfWeek.Tuesday:
            return "سه شنبه";
        case DayOfWeek.Wednesday:
            return "چهارشنبه";
        case DayOfWeek.Thursday:
            return "پنجشنبه";
        case DayOfWeek.Friday:
            return "جمعه";
    }
    return "Err";
}

public static string DateMahFarsi(string MaheSal)
{
    string NameSeason = "Err";
    switch (MaheSal)
    {
        case "01":
            NameSeason = "فروردین";
            break;
        case "02":
            NameSeason = "اردیبهشت";
            break;
        case "03":
            NameSeason = "خرداد";
            break;
        case "04":
            NameSeason = "تیر";
            break;
        case "05":
            NameSeason = "مرداد";
            break;
        case "06":
            NameSeason = "شهریور";
            break;
        case "07":
            NameSeason = "مهر";
            break;
        case "08":
            NameSeason = "آبان";
            break;
        case "09":
            NameSeason = "آذر";
            break;
        case "10":
            NameSeason = "دی";
            break;
        case "11":
            NameSeason = "بهمن";
            break;
        case "12":
            NameSeason = "اسفند";
            break;
    }
    return NameSeason;
}