static vs. instance versions of Regex.Match in C#

Question

I've noticed some code that uses the static method:

Regex.IsMatch([someRegexStr], [someInputStr])

Is it worth replacing it with the instance method? Like:

private readonly Regex myRegex = new Regex([someRegexStr]);

...

myRegex.IsMatch([someInputStr]);

Answer 1

One of the regular expression optimization recommendations in the following link: Regular Expression Optimization by Jim Mischel

For better performance on commonly used regular expressions, construct a Regex object and call its instance methods.

The article contains interesting topics such as caching regular expressions and compiling regular expressions along with optimization recommendations.

Answer 2

The last 15 regular expression internal representations created from the static call are cached.

I talk about this and the internal workings in "How .NET Regular Expressions Really Work."