C#读取路径下的所有文件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.IO;
using System.Collections;

namespace myTest0426
{
    class Program
    {

        static void Main(string[] args)
        {


            String path = @"F:\TEST";	    //获取路径下的所有文件名
            String[] fileNames = Directory.GetFiles(path, "*.txt");

	    //读取路径下的所有文件
            string train_text = ReadTxt(path,SelectRule);
            WriteTxt("F:\\TEST_WRITE\\a.txt", train_text);


                

            }
        }

      


        //文件读写
        private static bool SelectRule(string text)
        {
            return text.Length > 1 ? true : false;
        }

        private static void WriteTxt(string path, string text)
        {
            using (StreamWriter sw = new StreamWriter(path))
            {
                sw.Write(text);
            }
        }

        private static string ReadTxt(string path, Func<string, bool> selectRule)
        {
            StringBuilder text = new StringBuilder();
            string temp = string.Empty;
            DirectoryInfo folder = new DirectoryInfo(path);
            FileInfo[] files = folder.GetFiles("*.txt", SearchOption.AllDirectories);
            foreach (FileInfo file in files)
            {
                using (StreamReader sr = file.OpenText())
                {
                    while (sr.Peek() > 0)
                    {
                        temp = sr.ReadLine();
                        if (selectRule(temp))
                        {
                            text.AppendLine(temp);
                        }
                    }
                }
            }
            return text.ToString();
        }



    }
}