Search keyword highlight in ASP.Net

I am outputting a list of search results for a given string of keywords, and I开发者_开发百科 want any matching keywords in my search results to be highlighted. Each word should be wrapped in a span or similar. I am looking for an efficient function to do this.

E.g.

Keywords: "lorem ipsum"

Result: "Some text containing lorem and ipsum"

Desired HTML output: "Some text containing <span class="hit">lorem</span> and <span class="hit">ipsum</span>"

My results are case insensitive.

Here's what I've decided on. An extension function that I can call on the relevant strings within my page / section of my page:

public static string HighlightKeywords(this string input, string keywords)
{
    if (input == string.Empty || keywords == string.Empty)
    {
        return input;
    }

    string[] sKeywords = keywords.Split(' ');
    foreach (string sKeyword in sKeywords)
    {
        try
        {
            input = Regex.Replace(input, sKeyword, string.Format("<span class=\"hit\">{0}</span>", "$0"), RegexOptions.IgnoreCase);
        }
        catch
        {
            //
        }
    }
    return input;
}

Any further suggestions or comments?

try highlighter from Lucene.net

http://incubator.apache.org/lucene.net/docs/2.0/Highlighter.Net/Lucene.Net.Highlight.html

How to use:

http://davidpodhola.blogspot.com/2008/02/how-to-highlight-phrase-on-results-from.html

EDIT: As long as Lucene.net highlighter is not suitable here new link:

http://mhinze.com/archive/search-term-highlighter-httpmodule/

Use the jquery highlight plugin.

For highlighting it at server side

protected override void Render( HtmlTextWriter writer )
{
    StringBuilder html = new StringBuilder();
    HtmlTextWriter w = new HtmlTextWriter( new StringWriter( html ) );

    base.Render( w );

    html.Replace( "lorem", "<span class=\"hit\">lorem</span>" );

    writer.Write( html.ToString() );
}

You can use regular expressions for advanced text replacing.

You can also write the above code in an HttpModule so that it can be re used in other applications.

An extension to the answer above. (don't have enough reputation to give comment)

To avoid span from being replaced when search criteria were [span pan an a], the found word was replaced to something else than replace back... not very efficient though...

public string Highlight(string input)
{
    if (input == string.Empty || searchQuery == string.Empty)
    {
        return input;
    }

    string[] sKeywords = searchQuery.Replace("~",String.Empty).Replace("  "," ").Trim().Split(' ');
    int totalCount = sKeywords.Length + 1;
    string[] sHighlights = new string[totalCount];
    int count = 0;

    input = Regex.Replace(input, Regex.Escape(searchQuery.Trim()), string.Format("~{0}~", count), RegexOptions.IgnoreCase);
    sHighlights[count] = string.Format("<span class=\"highlight\">{0}</span>", searchQuery);
    foreach (string sKeyword in sKeywords.OrderByDescending(s => s.Length))
    {
        count++;
        input = Regex.Replace(input, Regex.Escape(sKeyword), string.Format("~{0}~", count), RegexOptions.IgnoreCase);
        sHighlights[count] = string.Format("<span class=\"highlight\">{0}</span>", sKeyword);
    }

    for (int i = totalCount - 1; i >= 0; i--)
    {
        input = Regex.Replace(input, "\\~" + i + "\\~", sHighlights[i], RegexOptions.IgnoreCase);
    }

    return input;
}