Search keyword highlight in ASP.Net C#

Question

Hi all,

I am outputting a list of search results for a given string of keywords, and I 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.

Many thanks, Tim

Answer 1

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/

Answer 2

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.

Answer 3

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?

Cheers, Tim