Create an index and define a text analyzer
// Ensures index backward compatibility
const LuceneVersion AppLuceneVersion = LuceneVersion.LUCENE_48;
// Construct a machine-independent path for the index
var basePath = Environment.GetFolderPath(
Environment.SpecialFolder.CommonApplicationData);
var indexPath = Path.Combine(basePath, "index");
using var dir = FSDirectory.Open(indexPath);
// Create an analyzer to process the text
var analyzer = new StandardAnalyzer(AppLuceneVersion);
// Create an index writer
var indexConfig = new IndexWriterConfig(AppLuceneVersion, analyzer);
using var writer = new IndexWriter(dir, indexConfig);
Add to the index
var source = new
{
Name = "Kermit the Frog",
FavoritePhrase = "The quick brown fox jumps over the lazy dog"
};
var doc = new Document
{
// StringField indexes but doesn't tokenize
new StringField("name",
source.Name,
Field.Store.YES),
new TextField("favoritePhrase",
source.FavoritePhrase,
Field.Store.YES)
};
writer.AddDocument(doc);
writer.Flush(triggerMerge: false, applyAllDeletes: false);
Construct a query
// Search with a phrase
var phrase = new MultiPhraseQuery
{
new Term("favoritePhrase", "brown"),
new Term("favoritePhrase", "fox")
};
Fetch the results
// Re-use the writer to get real-time updates
using var reader = writer.GetReader(applyAllDeletes: true);
var searcher = new IndexSearcher(reader);
var hits = searcher.Search(phrase, 20 /* top 20 */).ScoreDocs;
// Display the output in a table
Console.WriteLine($"{"Score",10}" +
$" {"Name",-15}" +
$" {"Favorite Phrase",-40}");
foreach (var hit in hits)
{
var foundDoc = searcher.Doc(hit.Doc);
Console.WriteLine($"{hit.Score:f8}" +
$" {foundDoc.Get("name"),-15}" +
$" {foundDoc.Get("favoritePhrase"),-40}");
}
Lucene.Net is a port of the Lucene search library, written in C# and targeted at .NET runtime users.