How do you run Lucene on .net?

Question

Lucene is an excellent search engine, but the .NET version is behind the official Java release (latest stable .NET release is 2.0, but the latest Java Lucene version is 2.4, which has more features).

How do you get around this?

Answer 1

One way I found, which was surprised could work: Create a .NET DLL from a Java .jar file! Using IKVM you can download Lucene, get the .jar file, and run:

ikvmc -target:library <path-to-lucene.jar>

which generates a .NET dll like this: lucene-core-2.4.0.dll

You can then just reference this DLL from your project and you're good to go! There are some java types you will need, so also reference IKVM.OpenJDK.ClassLibrary.dll. Your code might look a bit like this:

QueryParser parser = new QueryParser("field1", analyzer);
java.util.Map boosts = new java.util.HashMap();
boosts.put("field1", new java.lang.Float(1.0));
boosts.put("field2", new java.lang.Float(10.0));

MultiFieldQueryParser multiParser = new MultiFieldQueryParser
                      (new string[] { "field1", "field2" }, analyzer, boosts);
multiParser.setDefaultOperator(QueryParser.Operator.OR);

Query query = multiParser.parse("ABC");
Hits hits = isearcher.search(query);

I never knew you could have Java to .NET interoperability so easily. The best part is that C# and Java is "almost" source code compatible (where Lucene examples are concerned). Just replace System.Out with Console.Writeln :).

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Update: When building libraries like the Lucene highlighter, make sure you reference the core assembly (else you'll get warnings about missing classes). So the highlighter is built like this:

ikvmc -target:library lucene-highlighter-2.4.0.jar -r:lucene-core-2.4.0.dll