常用编码转换

//unicode转GB2312

 public static string UTF8ToGb2312(string str)
    {
        string gb2312info = string.Empty;
        Encoding utf8 = Encoding.UTF8;
        Encoding gb2312 = Encoding.GetEncoding("gb2312");
        byte[] unicodeBytes = utf8.GetBytes(str);
        byte[] asciiBytes = Encoding.Convert(utf8, gb2312, unicodeBytes);
        char[] asciiChars = new char[gb2312.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
        gb2312.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
        gb2312info = new string(asciiChars);
        return gb2312info;
    }