Returning multiple values from a method

Question

I can think of the following ways to return multiple values from a method (and one which splits into two methods)

private bool IsCarFaulty(Car car, out string fault)
{
  fault = string.Empty;
  return false;
}

---

private Tuple<bool, string> IsCarFaulty(Car car)
{
  return Tuple.Create(false, string.Empty);
}

---

private ResultAndMessage IsCarFaulty(Car car)
{
  return new ResultAndMessage(false, string.Empty);
}

---

private bool IsCarFaulty(Car car)
{
  return false;
}

private string GetCarFault(Car car)
{
  return string.Empty;
}

Basically my question is, are there situations where one is preferable over the other? If I take int.TryParse for an example. It uses an out parameter, but couldn't splitting it into two methods CanParse and Parse work just as well, if not better.

Answer 1

The problem with separate CanParse and Parse methods is that you have to pay the cost of parsing twice - once in CanParse and then again in Parse. This can be especially problematic when the parsing is quite complex and time-consuming (for example for types like DateTime).