class FileHelper

    {

        /// <summary>

        /// 检验文件路径是否合法

        /// </summary>

        /// <param name="path">文件路径</param>

        private static bool CheckPath(string path)

        {

            //正确格式：C:\Users\jcx\Desktop\Test.txt

            string pattern = @"\w{1}:([\\].+)*.+\.\w{3,}";

            Regex rg = new Regex(pattern);

            return rg.IsMatch(path);

        }

       /// <summary>

       /// 创建一个新的文本文件

       /// </summary>

        /// <param name="path">文件路径</param>

       /// <param name="content">写入到文本的内容</param>

        public static void CreateNewTxtFile(string path,string content)

        {

            if (!CheckPath(path))

            {

                throw new Exception("文件路径不合法");

            }

            //存在则删除

            if (File.Exists(path))

            {

                File.Delete(path);

            } 

            using (FileStream fs=new FileStream (path,FileMode.CreateNew,FileAccess.Write))

            {

                byte[] bt = Encoding.Default.GetBytes(content);

                fs.Write(bt,,bt.Length);

            } //using

        }

        /// <summary>

       /// 读取文本文件

       /// </summary>

       /// <param name="path">文件路径</param>

       /// <param name="readByte">指定每次读取字节数</param>

        /// <returns>读取的全部文本内容</returns>

        public static string ReadTxtFile(string path,long readByte)

        {

            if (!CheckPath(path))

            {

                throw new Exception("文件路径不合法");

            }

            StringBuilder result = new StringBuilder();

            using (FileStream fs=new FileStream (path,FileMode.Open,FileAccess.Read))

            {

                byte[] bt = new byte[readByte];

                while (fs.Read(bt,,bt.Length)>) //每次只从文件中读取部分字节数，一点点读

                {

                    string txt = Encoding.Default.GetString(bt);  //解码转换成字符串

                    result.AppendLine(txt);

                }

            } //using

            return result.ToString();

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            string path = @"C:\Users\jcx\Desktop\Test.txt";

            FileHelper.CreateNewTxtFile(path, "好好努力");

            string r = FileHelper.ReadTxtFile(path,);      //2个字节为一个汉字，一个汉字一个汉字的读

            Console.WriteLine(r);

        } // Main

    }