Should Guid.Empty Result in ArgumentException or ArgumentOutOfRangeException

Question

Imagine that you have a method with the following signature:

public void DoSomething(Guid id)

If Guid.Emtpy represents an illegal value, which Exception type would it be most appropriate to throw? ArgumentException or ArgumentOutOfRangeException?

I'm leaning slightly towards ArgumentException, since I don't think that all Guids except Guid.Empty is much of a range - it's a bit too inclusive: There is only one excluded member.

However, I am in no way determined that this should be the case, so I'd like to hear if anyone can provide arguments for one or the other?

I'm well aware that this is mainly a semantic discussion, but in the interest of good API design I'd still like to know whether there are clear cases for one or the other option.

Answer 1

Throw an InvalidArgumentException. That exactly follows the semantics you're after. You wouldn't throw an ArgumentOutOfRangeException if you expect an uint and all values except 0xffffffff are valid, would you?

Answer 2

I'd throw an ArgumentException. Its docs say:

The exception that is thrown when one of the arguments provided to a method is not valid.

which is exactly the scenario you describe. You want something along the lines of:

throw new ArgumentException("Guid.Empty is not a valid id", "id");

Answer 3

Saying that an empty value is out of range just seems wrong. As Guid.Empty is usually used when there is no defined value at all, there isn't really any value that can be outside of the range.

The situation is similar to when you use ArgumentNullException, except there is no specific exception for empty values. An ArgumentNullException would be misleading, so ArgumentException is a better fit.

Also consider if ApplicationException would be better. That's used for exceptions in the application rather than a class library.

Answer 4

AE.

Exactly what is the acceptable range of Guids your method is expecting?

Is CA72EE5A-5F26-11DE-BD28-13A156D89593 within the acceptable range, but D58B3112-5F26-11DE-B0D2-5FA156D89593 is right out?