/// <summary>
/// 多字段搜索(以空格，逗号等分隔符隔开)
/// </summary>
/// <param name="keyword"></param>
/// <returns></returns>
private TopDocs MulFieldsSearch(string keyword)
{
    TopDocs docs = null;
    int n = 100;
    SetOutput("正在检索关键字：" + keyword);
    try
    {
        BooleanClause.Occur[] flags=new BooleanClause.Occur[]{BooleanClause.Occur.MUST,BooleanClause.Occur.MUST};
        string[] fields = new string[] { "id", "contents" };
        string[] values = keyword.Trim().Split(new char[] { ' ', ',' }, StringSplitOptions.RemoveEmptyEntries);
        if (fields.Length != values.Length)
        {
            throw new Exception("字段和对应值不一致");
        }
        //MultiFieldQueryParser parser = new MultiFieldQueryParser(fields, new StandardAnalyzer());
        //parser.SetDefaultOperator(QueryParser.Operator.OR);//或者的关系
        //Query query = parser.Parse(keyword); 
        Query query = MultiFieldQueryParser.Parse(values, fields, flags, new StandardAnalyzer());
        Stopwatch watch = new Stopwatch();
        watch.Start();
 
        docs = searcher.Search(query, (Filter)null, n); //排序获取搜索结果
        watch.Stop();
        StringBuffer sb = "搜索完成,共用时：" + watch.Elapsed.Hours + "时 " + watch.Elapsed.Minutes + "分 " + watch.Elapsed.Seconds + "秒 " + watch.Elapsed.Milliseconds + "毫秒";
        SetOutput(sb);
    }
    catch (Exception ex)
    {
        SetOutput(ex.Message);
    }
    return docs;
}