Question

I have a number of user defined Regexes that I’m using to test some strings to see If I should exclude them.

private readonly IEnumerable<Regex> exclusions = <some user defined source>;

static bool Exclude(string value)
{
    return this.exclusions.Any(regex => regex.IsMatch(value);
}

I’m thinking, is there some way to compound the set of exclusions into a single combined exclusion Regex which would allow me to remove the iteration from the Exclude function, like this.

static bool Exclude(string value)
{
    return this.exclusion.IsMatch(value);
}

Is this approach feasible, would it have a potential performance benefit or is it just pushing the burden of iteration down into the Regex processor?

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EDIT

So, I could simply do,

var exclusion =
    new Regex(string.Join("|", exclusions.Select(e => e.ToString()));

Is there any more sophisticated option?

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EDIT 2

I’ve decided that since I have no control over the regular expressions, combining them blind is a naive approach, more likely to result in bugs than improved performance.

Answer 1

Logical OR:

regex1 | regex2 | ...