读写文本

        public static string ReadFile(string fileFullName)
        {
            if (!File.Exists(fileFullName)) 
                return string.Empty;

            using (FileStream fs = new FileStream(fileFullName, FileMode.Open, FileAccess.Read))
            {
                StreamReader sr = new StreamReader(fs, Encoding.Default);
                return sr.ReadToEnd();
            }
        }

        public static void WriteFile(string fileFullName, string input)
        {
            using (FileStream fs = new FileStream(fileFullName, FileMode.OpenOrCreate, FileAccess.Write))
            {
                StreamWriter sw = new StreamWriter(fs, Encoding.Default);
                sw.WriteLine(input);
                sw.Flush();
            }
        }