Random rnd = new Random();
DateTime fotoDate = new DateTime(rnd.Next(2010,2015),rnd.Next(1,12),rnd.Next(1,28),rnd.Next(0,23),rnd.Next(1,59),rnd.Next(1,59));
string randomName = "IMG" + fotoDate.ToString("yyyyMMdd") + "_" + rnd.Next(100,9999).ToString("0000") + ".jpg";