public string Valid(string CustomerRegisteredDate, string Name, string productId, string point) { String Error = ""; DateTime DateTemp; DateTime Minimum; if (productId.Length == 0) { Error = Error + "The ProductId may not be blank: "; } if (point.Length == 0) { Error = Error + "The point may not be negative: "; } if (Name.Length == 0) { Error = Error + "The name may not be blank: "; } if (Name.Length > 50) { Error = Error + "The name must contain less than 51 characters: "; } try { DateTemp = Convert.ToDateTime(CustomerRegisteredDate); Minimum = DateTime.Now.Date; Minimum = Minimum.AddMonths(-5); if (DateTemp > DateTime.Now.Date) { Error = Error + "the date cannot be in the future: "; } if (DateTemp < Minimum) { Error = Error + "the date cannot be in the very past: "; } } catch { Error = Error + "the date was not a valid date: "; } return(Error); }