class Program    {        static void Main(string[] args)        {            string path ="test.txt";            Write(path);            Console.WriteLine(Read(path));            Console.ReadKey();        }        public static void Write(string path)        {            using (FileStream fs = new FileStream(path, FileMode.Append))            {                StreamWriter sw = new StreamWriter(fs);                sw.WriteLine("Hello World!!!!");                sw.WriteLine("Hello World!!!!");                sw.Flush();                Console.WriteLine("写入成功！");            }        }        public static string Read(string path)        {            StreamReader sr = new StreamReader(path, Encoding.Default);            return sr.ReadToEnd();        }    }