Is it valid to create a static Regex object to be used by all threads in an ASP.NET application?

Question

I need to know if it's safe to create a static Regex object like this:

public static Regex s_Regex_ExtractEmails = new Regex(@"\b[A-Z0-9._%+-]+@(?:[A-Z0-9-]+\.)+[A-Z]{2,4}\b"); 

And call it statically from ASP.NET threads like this:

s_Regex_ExtractEmails.Matches("my email is [email protected]") 

Would this cause any problems?

I am doing this basically as an optimization so that the Regex object can be precompiled and reused.

Answer 1

Yes, Regex objects are thread-safe. From the docs:

The Regex class is immutable (read-only) and is inherently thread safe. Regex objects can be created on any thread and shared between threads.

You might want to consider using RegexOptions.Compiled too - although don't assume it'll help performance; measure!

Answer 2

I used a static Regex in a web app and it turned out to be a bottleneck as all requests used the same single instance.

I rewrote the function so a new Regex was created for each call and problem solved.

The app may have run faster at low usage levels but at very high levels of usage it didn't scale well.