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 expressions are valid as a lot of userse will mess op, with good intentions though.

I can of course do a Regex.IsMatch() inside a try/catch and see if it blows up that way, but are there any smarter ways of doing it? Speed is not an issue as such, I just prefer to avoid throwing exceptions for no reason.

Answer 1

I think exceptions are OK in this case.

Just make sure to shortcircuit and eliminate the exceptions you can:

private static bool IsValidRegex(string pattern)
{
    if (string.IsNullOrWhiteSpace(pattern)) return false;

    try
    {
        Regex.Match("", pattern);
    }
    catch (ArgumentException)
    {
        return false;
    }

    return true;
}

Answer 2

As long as you catch very specific exceptions, just do the try/catch.

Exceptions are not evil if used correctly.