Code
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MyLuceneNet.Functions;

namespace MyLuceneNet
{
    public partial class SearchForm : Form
    {
        //Lucene方法类
        LuceneOperate luceneOp;
        /// <summary>
        /// 构造函数
        /// </summary>
        public SearchForm()
        {
            InitializeComponent();           
        }
        /// <summary>
        /// 窗体加载方法
        /// <para>窗体加载时，创建Lucene方法类LuceneOperate的实例</para>
        /// <para>此LuceneOperate构造函数中的路径由folderBrowserDialog1选择</para>
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void SearchForm_Load(object sender, EventArgs e)
        {
            if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
            {
                luceneOp = new LuceneOperate(folderBrowserDialog1.SelectedPath);
            }
        }
        /// <summary>
        /// 点击查询按钮，则根据textBox查询内容文件的内容进行查询
        /// <para>查询结果显示到listBox文件中</para>
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button查询_Click(object sender, EventArgs e)
        {
            listBox文件.DataSource = luceneOp.GetResults(textBox查询内容.Text.Trim(), "Contents");
        }
        /// <summary>
        /// 生成索引按钮，调用生成索引的方法
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button生成索引_Click(object sender, EventArgs e)
        {
            if (luceneOp.CreateIndex())
            {
                MessageBox.Show("索引生成成功！", "索引生成", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("索引生成失败！", "索引生成", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }

    }
}

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

namespace MyLuceneNet.Functions
{
    public class LuceneOperate
    {
        //索引路径
        private string indexPath;
        //文件路径
        private string filesPath;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="_indexPath">传入的文件路径</param>
        public LuceneOperate(string _filesPath)
        {
            //文件路径
            filesPath = _filesPath;
            //索引保存路径
            indexPath = _filesPath + "\\Index";  
        }
        /// <summary>
        /// 创建索引
        /// </summary>
        /// <returns>返回成功情况(true,false)</returns>
        public bool CreateIndex()
        {
            try
            {        
                //建立一个索引书写器
                IndexWriter indxWritr = new IndexWriter(indexPath, new StandardAnalyzer(), true);
                InitIndex(filesPath, indxWritr);
                //索引优化
                indxWritr.Optimize();
                //关闭索引读写器
                indxWritr.Close();
                return true;
            }
            catch
            {
                return false;
            }
        }
        /// <summary>
        /// 初始的索引(未经优化)
        /// </summary>
        /// <param name="_filesPath">文件的路径</param>
        /// <param name="_indxWritr">索引书写器</param>
        private void InitIndex(string _filesPath, IndexWriter _indxWritr)
        {
            DirectoryInfo dirInfo = new DirectoryInfo(_filesPath);
            /*
             * 注释掉了遍历子文件夹的文件的
             * */
            //foreach (DirectoryInfo dirin in dirInfo.GetDirectories())
            //    InitIndex(dirin.FullName, _indxWritr);
            foreach (FileInfo f in dirInfo.GetFiles())
            {
                Document doc = new Lucene.Net.Documents.Document();
                //文件名
                doc.Add(new Field("FileName", f.FullName, Field.Store.YES, Field.Index.UN_TOKENIZED));
                //文件内容
                doc.Add(new Field("Contents", new System.IO.StreamReader(f.FullName, System.Text.Encoding.Default)));
                _indxWritr.AddDocument(doc);
            }
        }
        /// <summary>
        /// 得到结果的string的集合
        /// </summary>
        /// <param name="content">所要搜索的内容</param>
        /// <param name="field">搜索的field范围</param>
        /// <returns>结果集合</returns>
        public List<string> GetResults(string content,string field)
        {
            Hits hits = GetHits(content, field);
            List<string> Results = new List<string>();
            for (int i = 0; i < hits.Length(); i++)
            {
                Results.Add(hits.Doc(i).Get(field));
            }
            return Results;
        }
        /// <summary>
        /// 得到Hits,GetResults的辅助类
        /// </summary>
        /// <param name="content">所要搜索的内容</param>
        /// <param name="field">field</param>
        /// <returns>结果集合</returns>
        private Hits GetHits(string content,string field)
        {
            //打开索引，索引目录为程序刚开始选择的路径+"\\Index"
            IndexReader indxRedr = IndexReader.Open(indexPath);
            IndexSearcher indxSercr = new IndexSearcher(indxRedr);
            QueryParser parser = new QueryParser(field, new StandardAnalyzer());
            Query q = parser.Parse(content);
            Hits hits = indxSercr.Search(q);
            return hits;
        }
    }
}