Beginner RegEx Replace Performance Question

Question

I have this simple regex replace based routine, is there anyway to improve its performance (and maybe also its elegance?)

public static string stripshrapnel(string str)
{
        string newstr = str.Trim();
        newstr = Regex.Replace(newstr, @"-", "");
        newstr = Regex.Replace(newstr, @"'", "");
        newstr = Regex.Replace(newstr, @",", "");
        newstr = Regex.Replace(newstr, @"""", "");
        newstr = Regex.Replace(newstr, @"\?", "");
        newstr = Regex.Replace(newstr, @"\#", "");
        newstr = Regex.Replace(newstr, @"\;", "");
        newstr = Regex.Replace(newstr, @"\:", "");
        //newstr = Regex.Replace(newstr, @"\(", "");
        //newstr = Regex.Replace(newstr, @"\)", "");
        newstr = Regex.Replace(newstr, @"\+", "");
        newstr = Regex.Replace(newstr, @"\%", "");
        newstr = Regex.Replace(newstr, @"\[", "");
        newstr = Regex.Replace(newstr, @"\]", "");
        newstr = Regex.Replace(newstr, @"\*", "");
        newstr = Regex.Replace(newstr, @"\/", "");
        newstr = Regex.Replace(newstr, @"\\", "");
        newstr = Regex.Replace(newstr, @"&amp;", "&");
        newstr = Regex.Replace(newstr, @"&amp", "&");
        newstr = Regex.Replace(newstr, @"&nbsp;", " ");
        newstr = Regex.Replace(newstr, @"&nbsp", " ");
        return newstr;
}

Thank you, Matt

Gumbo · Accepted Answer · 2009-11-08 11:18:59Z

9

You can combine most of the expressions until you end up with only three:

public static string stripshrapnel(string str)
{
        string newstr = str.Trim();
        newstr = Regex.Replace(newstr, @"[-',""?#;:+%[\]*/\\\\]", "");
        newstr = Regex.Replace(newstr, @"&amp;?", "&");
        newstr = Regex.Replace(newstr, @"&nbsp;?", " ");
        return newstr;
}

answered Nov 8, 2009 at 11:18

Gumbo

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3 Comments

WickedW Over a year ago

Fantastic Gumbo!, thank you, does anyone have any ideas how much faster this would be (a rough %?)?

TrueWill Over a year ago

@WickedW: Is the current performance unacceptable? If so, have you profiled the application to determine if this is a bottleneck? It's generally best to avoid premature optimization. (Although I would definitely look into replacing your original code with Gumbo's.)

Gumbo Over a year ago

@WickedW: I don’t expect it to be that much faster since it does the same work but only in a different way. But why don’t you benchmark it yourself?

ase · Accepted Answer · 2009-11-08 11:20:03Z

3

Since you are using zero regex features maybe there is another way. It seems like C# has a Replace method for strings, use that instead, I imagine that there is a lot of extra power used when doing regex instead of a simple replace.

answered Nov 8, 2009 at 11:20

ase

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1 Comment

Henk Holterman Over a year ago

String.Replace does not have char-sets and would need similar code as in the question. Gumbo's solution is much faster and more readable.

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