How convert Gregorian date to Persian date?

Use the PersianCalendar:

string GregorianDate = "Thursday, October 24, 2013";
DateTime d = DateTime.Parse(GregorianDate);
PersianCalendar pc = new PersianCalendar();
Console.WriteLine(string.Format("{0}/{1}/{2}", pc.GetYear(d), pc.GetMonth(d), pc.GetDayOfMonth(d)));