ToShamsiDate

/// <summary>
/// Convert DateTime to Shamsi Date (YYYY/MM/DD)
/// </summary>
public static string ToShamsiDateYMD(this DateTime date)
{
    System.Globalization.PersianCalendar PC = new System.Globalization.PersianCalendar();
    int intYear = PC.GetYear(date);
    int intMonth = PC.GetMonth(date);
    int intDay = PC.GetDayOfMonth(date);
    return (intYear.ToString() + "/" + intMonth.ToString() + "/" + intDay.ToString());
}
/// <summary>
/// Convert DateTime to Shamsi Date (DD/MM/YYYY)
/// </summary>
public static string ToShamsiDateDMY(this DateTime date)
{
    System.Globalization.PersianCalendar PC = new System.Globalization.PersianCalendar();
    int intYear = PC.GetYear(date);
    int intMonth = PC.GetMonth(date);
    int intDay = PC.GetDayOfMonth(date);
    return (intDay.ToString() + "/" + intMonth.ToString() + "/" + intYear.ToString());
}
/// <summary>
/// Convert DateTime to Shamsi String 
/// </summary>
public static string ToShamsiDateString(this DateTime date)
{
    System.Globalization.PersianCalendar PC = new System.Globalization.PersianCalendar();
    int intYear = PC.GetYear(date);
    int intMonth = PC.GetMonth(date);
    int intDayOfMonth = PC.GetDayOfMonth(date);
    DayOfWeek enDayOfWeek = PC.GetDayOfWeek(date);
    string strMonthName, strDayName;
    switch (intMonth)
    {
        case 1:
            strMonthName = "فروردین";
            break;
        case 2:
            strMonthName = "اردیبهشت";
            break;
        case 3:
            strMonthName = "خرداد";
            break;
        case 4:
            strMonthName = "تیر";
            break;
        case 5:
            strMonthName = "مرداد";
            break;
        case 6:
            strMonthName = "شهریور";
            break;
        case 7:
            strMonthName = "مهر";
            break;
        case 8:
            strMonthName = "آبان";
            break;
        case 9:
            strMonthName = "آذر";
            break;
        case 10:
            strMonthName = "دی";
            break;
        case 11:
            strMonthName = "بهمن";
            break;
        case 12:
            strMonthName = "اسفند";
            break;
        default :
            strMonthName = "";
            break;
    }

    switch (enDayOfWeek)
    {
        case DayOfWeek.Friday:
            strDayName = "جمعه";
            break;
        case DayOfWeek.Monday:
            strDayName = "دوشنبه";
            break;
        case DayOfWeek.Saturday:
            strDayName = "شنبه";
            break;
        case DayOfWeek.Sunday:
            strDayName = "یکشنبه";
            break;
        case DayOfWeek.Thursday:
            strDayName = "پنجشنبه";
            break;
        case DayOfWeek.Tuesday:
            strDayName = "سه شنبه";
            break;
        case DayOfWeek.Wednesday:
            strDayName = "چهارشنبه";
            break;
        default:
            strDayName = "";
            break;
    }

    return (string.Format("{0} {1} {2} {3}", strDayName, intDayOfMonth, strMonthName, intYear));
}

string strShamsiDate1 = DateTime.Now.ToShamsiDateYMD();
string strShamsiDate2 = DateTime.Now.ToShamsiDateDMY();
string strShamsiDate3 = DateTime.Now.ToShamsiDateString();