A long time ago, I wrote a blog post about the problems with String.Trim(). I’m happy to see that all three issues have been addressed in the .NET Framework 4.0.
To start with, Trim() will now be consistent with Char.IsWhiteSpace(). Theoretically, this is a breaking change, but I don’t expect many programs to have a problem with this change. Note that the change is very well documented in the online help.
Secondly, the code of Trim() has been cleaned up considerably. A string that consists entirely of whitespace is no longer scanned twice. I haven’t done any benchmarks, but I expect the performance to be at least as good as for the same function in .NET 2.0 – 3.5.
Last but not least, the frequent abuse of the Trim() function to simply validate strings will greatly decrease with the introduction of the static IsNullOrWhitespace(string value) function, which is much faster than calling Trim().
It’s a small detail, compared to all the other goodies .NET 4.0 brings, but a good addition to the toolbox nonetheless.