C# 读写TXT文件出现乱码

 context = System.IO.File.ReadAllText(filename, Encoding.GetEncoding("gb2312"));

 

 System.IO.File.AppendAllText(@"F:/Coding/AddTxtFile/xqj/0000.txt", context, Encoding.GetEncoding("gb2312") );

 

用Encoding.UTF8不行，必须用Encoding.GetEncoding("gb2312")。