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I'm using Lucene.net to implement fulltext search feature in an Asp.net application. The search result page should high light the match items. I got the instance of Lucene.Net.Search.Hits and used .Doc(int i) method to get Lucene Document.

But I don't know how to get the position of match item by existing method or property of some Lucene class. Does Lucene.net provide any feature to support high light query string?

Archer Chen
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2 Answers2

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You can use Highlighter or FastVectorHighlighter which can be found in contrib

L.B
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As the previous answerer said, you should use either Highlighter or FastVectorHighlighter from contrib.

Here's an example of using Highlighter lib to get highlighted fragments:

Formatter formatter = new SimpleHTMLFormatter("<span><b>", "</b></span>");
Lucene.Net.Highlight.Scorer scorer = new QueryScorer(query, field);
Lucene.Net.Highlight.Encoder encoder = new SimpleHTMLEncoder();
var highlighter = new Highlighter(formatter, encoder, scorer);
highlighter.SetTextFragmenter(new SimpleFragmenter(100));

string[] fragments = 
    highlighter.GetBestFragments(DefaultAnalyzer, field, doc.Get(field), 3);

Some Highlighter-related gotchas:

  • To highlight a field, it should be added to index with Field.Store.YES option

  • Your query should be rewritten before passing it to highlighter

  • The analyzer you pass to highlighter should be the same you use for indexing and searching
buru
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  • `To highlight a field, it should be added to index with Field.Store.YES option` You don't need to store if you plan to highlight an extarnal source such as original (text) file indexed. – L.B Nov 11 '11 at 16:21
  • @L.B. still, it can be a gotcha if you want to highlight document field's text and don't know about such highlighter requirement. – buru Nov 13 '11 at 15:04