private string GenRN() { try { PurchaseReturn lastReturn = return_repo.GetLast(); //PurchaseReturn lastReturn = context.PurchaseReturns.LastOrDefault(); string value = lastReturn.ReturnNumber; string number = Regex.Match(value, "[0-9]+$").Value; return(value.Substring(0, value.Length - number.Length) + (long.Parse(number) + 1).ToString().PadLeft(number.Length, '0')); } catch (NullReferenceException e) { return("PRN0000001"); } }