string.IsNullOrEmpty() vs string.NotNullOrEmpty()

Question

I\'m curious if any developers use string.IsNullOrEmpty() more often with a negative than with a positive

e.g.

if (!string.IsNullOrEmpty())

Answer 1

For those logicians out there, !string.IsNullOrEmpty is not equivalent to string.IsNotNullOrEmpty. @Guffa has it correct. Using DeMorgan's law, it would have to be string.IsNotNullAndNotEmpty to be equivalent.

¬(null ∨ empty) ⇔ ¬null ∧ ¬empty

¬(null ∨ empty) ≠ ¬null ∨ empty

The point here, I guess, is that the way it is currently is unambiguous, where as making the opposite unambiguous would be cumbersome.

Answer 2

That is the most common usage I have seen.

Answer 3

Personally I prefer to cater for the non negated scenario first. It just makes sense to me to do the true part first and then the false. Comes down to personal style.

Answer 4

I always create an extension method for "HasContent()" which generally makes sense, follows the "positive" specifications, and saves on code bloat because I use it much more often than its counterpart:

public static bool HasContent(this string s) {
    return !string.IsNullOrEmpty(s);
}

Answer 5

Perhaps because then the name would have to be the lengthy IsNotNullAndNotEmpty to be as specific.

Answer 6

Of course you could always use string.IsNullOrWhiteSpace(string) now instead of string .IsNullOrEmpty(string) from .NET 4.0