RegExOptions

Use the correct RegexOption when defining the regular expression.

When defining a regular expression, one can define RegexOptions, which enable fine-grained control over the regular expression engine. That also works with the newly introduced RegexGenerator introduced in .net 7, as they use the same attributes.

Compiled

This flags (which is the default for RegexGenerator in .net7, so you do not have to provide that argument for them) enables the compilation of the regular expression into the MSIL code of the application. That brings performance improvements in trade-off in expense of a bigger startup time of your application. There are only small scenarios, where this flag does not make sense.

ExplicitCapture

If you don’t work with capture groups, you can safely provide this flag as this tells the regex engine not to look for implicit captures. Explicit captures are something like this: ?<groupname>.

Defining multiple values

As RegexOption are defined as flags, you can provide multiple arguments delimited by the | characters (bitwise or).

public class RegexBenchmark
{
    private const string Sentence = "Hello this is an example of stock tips!";
    private const string RegexString = @"(\W|^)stock\stips(\W|$)";
    private static readonly Regex StockTips = new(RegexString);
    private static readonly Regex StockTipsCompiled = new(RegexString, RegexOptions.Compiled);
    private static readonly Regex StockTipsExplicitCapture = new(RegexString, RegexOptions.ExplicitCapture);
    private static readonly Regex StockTipsAllCombined = new(RegexString,
        RegexOptions.Compiled | RegexOptions.ExplicitCapture);

    [Benchmark(Baseline = true)]
    public bool HasMatch() => StockTips.IsMatch(Sentence);

    [Benchmark]
    public bool HasMatchCompiled() => StockTipsCompiled.IsMatch(Sentence);

    [Benchmark]
    public bool HasMatchExplicitCapture() => StockTipsExplicitCapture.IsMatch(Sentence);

    [Benchmark]
    public bool HasMatchCombined() => StockTipsAllCombined.IsMatch(Sentence);
}

Results:

|                  Method |       Mean |    Error |   StdDev | Ratio |
|------------------------ |-----------:|---------:|---------:|------:|
|                HasMatch | 1,348.4 ns | 17.48 ns | 16.35 ns |  1.00 |
|        HasMatchCompiled |   650.0 ns |  3.59 ns |  3.36 ns |  0.48 |
| HasMatchExplicitCapture | 1,062.4 ns |  5.50 ns |  5.14 ns |  0.79 |
|        HasMatchCombined |   528.0 ns |  3.09 ns |  2.89 ns |  0.39 |