EdgeNgramAnalyzer.cs

using System.IO;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.NGram;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Util;
using Sitecore.Configuration;

namespace Sitecore.ContentSearch.LuceneProvider.Analyzers
{
    public class EdgeNgramAnalyzer : Lucene.Net.Analysis.Analyzer
    {
        public override TokenStream TokenStream(string fieldName, TextReader reader)
        {
            var defaultAnalyzer = new LowerCaseFilter(new StandardTokenizer(Version.LUCENE_30, reader)) as TokenStream;
            var minLength = Settings.GetIntSetting("Sitecore.ContentSearch.Ngrams.MinLength", 3);
            var maxLength = Settings.GetIntSetting("Sitecore.ContentSearch.Ngrams.MaxLength", 20);

            var ngramsFront = new EdgeNGramTokenFilter(defaultAnalyzer, Side.FRONT, minLength, maxLength);
            return new EdgeNGramTokenFilter(ngramsFront, Side.BACK, minLength, maxLength);
        }
    }
}