November 20, 2008
String.IsNullOrEmpty - performance considerations, bugs
I once read that .Net's String.IsNullOrEmpty performs better, and is safer, than just checking to see if a particular string has an empty value. I.e. replace if (myString == "") or if (myString.Equals(string.Empty)) or if (myString.Length == 0) with if (String.IsNullOrEmpty(myString)). It is certainly easy to read, and points out that the string should really be checked for null value before doing anything else.
Wanting to double-check my memory before recommending this method to a colleague, I found a few very interesting blog posts that suggest to me that I should avoid its usage:
- DANGER ! String.IsNullOrEmpty can lead to runtime Null exceptions !!, it looks like this isn't fully explained yet. Might not be an issue in .Net 3.0/3.5 frameworks, but I'm still using .Net 2.0, so it is best to heed this warning.
- string.IsNullOrEmpty Samples, it seems the performance is good, but not the best. So where performance matters, go with the longest, safest version:
if (myString == null || myString.Length == 0)
Comments
Rob — March 10, 2009
As well as not being an issue for .Net 3/3.5 as you suggest, it was also fixed a while ago, for .NET 2. It was fixed by a hotfix dated September 3, 2007 [http://support.microsoft.com/kb/940900/] and included in SP1 [http://support.microsoft.com/kb/945757].
So while the second issue may affect some people (as you say, where performance matters, and where it matters over readability), the first is no longer something to worry about (or has been for a while)