Question

What is the best way to produce a highlighted string found within another string?

I want to ignore all character that are not alphanumeric but retain them in the final output.

So for example a search for ‘PC3000’ in the following 3 strings would give the following results:

   ZxPc 3000L = Zx<font color='red'>Pc 3000</font>L

   ZXP-C300-0Y  =  ZX<font color='red'>P-C300-0</font>Y

   Pc3 000  =   <font color='red'>Pc3 000</font>

I have the following code but the only way i can highlight the search within the result is to remove all the whitespace and non alphanumeric characters and then set both strings to lowercase. I’m stuck!

public string Highlight(string Search_Str, string InputTxt)
    {

        // Setup the regular expression and add the Or operator.
        Regex RegExp = new Regex(Search_Str.Replace(" ", "|").Trim(), RegexOptions.IgnoreCase);

        // Highlight keywords by calling the delegate each time a keyword is found.
        string Lightup = RegExp.Replace(InputTxt, new MatchEvaluator(ReplaceKeyWords));

        if (Lightup == InputTxt)
        {
            Regex RegExp2 = new Regex(Search_Str.Replace(" ", "|").Trim(), RegexOptions.IgnoreCase);
            RegExp2.Replace(" ", "");

            Lightup = RegExp2.Replace(InputTxt.Replace(" ", ""), new MatchEvaluator(ReplaceKeyWords));

            int Found = Lightup.IndexOf("<font color='red'>");

            if (Found == -1)
            {
                Lightup = InputTxt;
            }

        }

        RegExp = null;
        return Lightup;
    }

    public string ReplaceKeyWords(Match m)
    {
        return "<font color='red'>" + m.Value + "</font>";
    }

Thanks guys!

Answer 1

Alter your search string by inserting an optional non-alphanumeric character class ([^a-z0-9]?) between each character. Instead of PC3000 use

P[^a-z0-9]?C[^a-z0-9]?3[^a-z0-9]?0[^a-z0-9]?0[^a-z0-9]?0

This matches Pc 3000, P-C300-0 and Pc3 000.