If you want the regular expression to run faster , you can set the RegexOptions.Compiled value to the regex constructor. This will compile the regex in to their own assembly which will run a little faster.

Below is a sample code snippet demonstrating the usage of RegexOptions.Compiled.

//  Validating a Zip codes in C# using Regular Expression
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string GKZipCode = @"^\d{5}(-?\d{4})?$";
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Regex regex = new Regex(GKZipCode, RegexOptions.Compiled);
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bool Matching = regex.IsMatch("15689");
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Console.WriteLine(Matching);
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Console.ReadLine();