StreamReader SReader = new StreamReader(“C：\1.txt”, Encoding.Default);//路径与编码      str = SReader.ReadToEnd();      SReader.Close(); FileStream fs1 = new FileStream(“C：\1.txt”, FileMode.Create, FileAccess.Write);//创建写入文件，此方法创建文档，如存在则覆盖      StreamWriter sw = new StreamWriter(fs1,Encoding.Default);//对象与编码      sw.WriteLine(str);//开始写入值