Can I test if a regex is valid in C# without throwing exception

Question

I allow users to enter a regular expression to match IP addresses, for doing an IP filtration in a related system. I would like to validate if the entered regular expression

Answer 1

Not without a lot of work. Regex parsing can be pretty involved, and there's nothing public in the Framework to validate an expression.

System.Text.RegularExpressions.RegexNode.ScanRegex() looks to be the main function responsible for parsing an expression, but it's internal (and throws exceptions for any invalid syntax anyway). So you'd be required to reimplement the parse functionality - which would undoubtedly fail on edge cases or Framework updates.

I think just catching the ArgumentException is as good an idea as you're likely to have in this situation.