Insert at index of search term substring

Question

I am trying to highlight search terms in display results. Generally it works OK based on code found here on SO. My issue with it is that it replaces the substring with the search term, i.e. in this example it will replace "LOVE" with "love" (unacceptable). So I was thinking I probably want to find the index of the start of the substring, do an INSERT of the opening tag, and do similar at the end of the substring. As yafs may be quite long I'm also thinking I need to integrate stringbuilder into this. Is this do-able, or is there a better way? As always, thank you in advance for your suggestions.

string yafs = "Looking for LOVE in all the wrong places...";
string searchTerm = "love";

yafs = yafs.ReplaceInsensitive(searchTerm, "<span style='background-color: #FFFF00'>" 
+  searchTerm + "</span>");

Don't all those websites use Javascript to do that on client side? — Thomas Weller, Mar 27 '14 at 13:24
Is your string already HTML before you do the replacement? If so, be careful with simple replacements. If someone is searching for "html" (or other html tags), your complete website will be broken. — Thomas Weller, Mar 27 '14 at 13:45
thanx for the tip. in this case it is preformatted text, no html involved. — Darkloki, Mar 27 '14 at 13:52

y.aoki · Accepted Answer · 2014-03-28T14:57:18.267

1

how about this:

public static string ReplaceInsensitive(string yafs, string searchTerm) {
    return Regex.Replace(yafs, "(" + searchTerm + ")", "<span style='background-color: #FFFF00'>$1</span>", RegexOptions.IgnoreCase);
}

update:

public static string ReplaceInsensitive(string yafs, string searchTerm) {
    return Regex.Replace(yafs,
        "(" + Regex.Escape(searchTerm) + ")", 
        "<span style='background-color: #FFFF00'>$1</span>",
        RegexOptions.IgnoreCase);
}

edited Mar 28 '14 at 14:57

answered Mar 27 '14 at 13:33

y.aoki

51
1
4

1

And if someone is searching for `.*`, everything is gone? – Thomas Weller Mar 27 '14 at 13:47
Thanks to all. Other options may work but this appears simplest and so far it test fine. – Darkloki Mar 27 '14 at 13:50
oops, must escape in that case...sorry – y.aoki Mar 27 '14 at 13:55

DGibbs · Answer 2 · 2014-03-27T13:56:23.707

Does what you need:

static void Main(string[] args)
{
    string yafs = "Looking for LOVE in all the wrong love places...";
    string searchTerm = "LOVE";

    Console.Write(ReplaceInsensitive(yafs, searchTerm));
    Console.Read();
}

private static string ReplaceInsensitive(string yafs, string searchTerm)
{
    StringBuilder sb = new StringBuilder();
    foreach (string word in yafs.Split(' '))
   {
        string tempStr = word;
        if (word.ToUpper() == searchTerm.ToUpper())
        {
            tempStr = word.Insert(0, "<span style='background-color: #FFFF00'>");
            int len = tempStr.Length;
            tempStr = tempStr.Insert(len, "</span>");
        }

        sb.AppendFormat("{0} ", tempStr);
    }

    return sb.ToString();
}

Gives:

Looking for LOVE in all the wrong love places...

Apologies, didn't realise there would be multiple instances of the word in the string. Updated. — DGibbs, Mar 27 '14 at 13:55

score 0 · Answer 3 · answered Mar 27 '14 at 13:29

Check this code

    private static string ReplaceInsensitive(string text, string oldtext,string newtext)
    {
        int indexof = text.IndexOf(oldtext,0,StringComparison.InvariantCultureIgnoreCase);
        while (indexof != -1)
        {
            text = text.Remove(indexof, oldtext.Length);
            text = text.Insert(indexof, newtext);


            indexof = text.IndexOf(oldtext, indexof + newtext.Length ,StringComparison.InvariantCultureIgnoreCase);
        }

        return text;
    }

Insert at index of search term substring

3 Answers3