VS代码中的Encoding.ASCII并不是ANSI编码的意思；
使用GB2312 以代表ANSI编码
string fileName = "D:\\1234.txt";
StreamWriter sw = new StreamWriter(fileName,false, Encoding.GetEncoding("GB2312"));
sw.WriteLine("col1,col2,col3");
sw.WriteLine("繁體中文,2,3");
sw.WriteLine("简体中文,2,3");
sw.WriteLine("English,2,3");
sw.Close();
sw.Dispose();
