CODEWITHSUNDEEP
c#regex
jimbo
jimbo

Reputation: 611

general speed issues when comparing strings using RegEx

Is there anyway of improving the speed / efficiency of this method? It is called tens of thousands of time in my code, and is slowing down the system I am developing.

Basically, 'Field' has a 'Name' and a 'Value' and I need to check if it matches the name/value of the corresponding property in my class. Field.Value may also be a regular expression. I imagine the regex is slowing things down a bit.

    private bool FieldMatch(Field field)
    {
        var propValue = GetPropertyValue(field.Name);
        var regEx = new Regex(field.Value, RegexOptions.IgnoreCase);
        var stringMatch = string.Compare(propValue, field.Value, StringComparison.InvariantCultureIgnoreCase )
        return (stringMatch == 0) || regEx.IsMatch(propValue);
    }

Upvotes: 0

Views: 55

Answers (1)

jimbo
jimbo

Reputation: 611

I have two solutions to this issue.

One is to add a pre-compiled Regex to the Field class like so:

public class Field
{

    public string Name { get; set; } // Should ultimately be an enum.

    public string Value { get; set; }

    public Regex RegexValue
    {
        get {
            return _regexValue ?? (_regexValue = 
                new Regex(Value, RegexOptions.Compiled | RegexOptions.IgnoreCase));
        }
    }

    private Regex _regexValue;

}

private bool FieldMatch(Field field)
{
    var propValue = GetPropertyValue(field.Name);
    var stringMatch = string.Compare(propValue, field.Value, StringComparison.InvariantCultureIgnoreCase);
    return (stringMatch == 0) || field.RegexValue.IsMatch(propValue);
}

The other is to use the static Regex like so:

  private bool FieldMatch(Field field)
    {
        var propValue = GetPropertyValue(field.Name);
        var stringMatch = string.Compare(propValue, field.Value,                     StringComparison.InvariantCultureIgnoreCase);
        return (stringMatch == 0) || Regex.IsMatch(propValue, field.Value);
    }

Which one is quickest depends on the scale of the system, but both are a very good improvement over the previous solution

Upvotes: 1

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