怎么判断文本文件编码啊，根据BYTE前一些字节？或者读取后转换？
https://social.msdn.microsoft.com/Forums/vstudio/en-US/b172cd4d-25fe-4696-8c0f-37226c053d71/how-to-detect-encoding-file-in-ansi-utf8-and-utf8-without-bom?forum=csharpgeneralhttp://stackoverflow.com/questions/4520184/how-to-detect-the-character-encoding-of-a-text-file