These codes are How to use Lucence.net

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers;
using Lucene.Net.Search;
using Lucene.Net.Store;

namespace Basic_Concepts
{
    class Program
    {
        static void Main(string[] args)
        {
            //Setup indexer

            Directory directory = FSDirectory.GetDirectory("LuceneIndex");
            Analyzer analyzer = new StandardAnalyzer();
            IndexWriter writer = new IndexWriter(directory, analyzer);

            IndexReader red = IndexReader.Open(directory);
            int totDocs = red.MaxDoc();
            red.Close();

            //Add documents to the index
            string text = String.Empty;
            Console.WriteLine("Enter the text you want to add to the index:");
            Console.Write(">");
            int txts = totDocs;
            int j = 0;
            while ((text = Console.ReadLine()) != String.Empty)
            {
                AddTextToIndex(txts++, text, writer);
                j++;
                Console.Write(">");
            }

            
            writer.Optimize();
            //Close the writer
            writer.Flush();
            writer.Close();

            Console.WriteLine(j + " lines added, "+txts+" documents total");

            //Setup searcher
            IndexSearcher searcher = new IndexSearcher(directory);
            QueryParser parser = new QueryParser("postBody", analyzer);


            Console.WriteLine("Enter the search string:");
            Console.Write(">");

            while ((text = Console.ReadLine()) != String.Empty)
            {
                Search(text, searcher, parser);
                Console.Write(">");
            }

            //Clean up everything
            searcher.Close();
            directory.Close();
        }

        private static void Search(string text, IndexSearcher searcher, QueryParser parser)
        {
            //Supply conditions
            Query query = parser.Parse(text);

            //Do the search
            Hits hits = searcher.Search(query);

            //Display results
            Console.WriteLine("Searching for '" + text + "'");
            int results = hits.Length();
            Console.WriteLine("Found {0} results", results);
            for (int i = 0; i < results; i++)
            {
                Document doc = hits.Doc(i);
                float score = hits.Score(i);
                Console.WriteLine("--Result num {0}, score {1}", i + 1, score);
                Console.WriteLine("--ID: {0}", doc.Get("id"));
                Console.WriteLine("--Text found: {0}" + Environment.NewLine, doc.Get("postBody"));
            }
        }

        private static void AddTextToIndex(int txts, string text, IndexWriter writer)
        {
            Document doc = new Document();
            doc.Add(new Field("id", txts.ToString(), Field.Store.YES, Field.Index.UN_TOKENIZED));
            doc.Add(new Field("postBody", text, Field.Store.YES, Field.Index.TOKENIZED));
            writer.AddDocument(doc);
        }
    }
}