Unicode编码转换为字符串

public static string ToGB2312(string str)
        {
            string r = "";
            MatchCollection mc = Regex.Matches(str, @"\\u([\w]{2})([\w]{2})", RegexOptions.Compiled | RegexOptions.IgnoreCase);
            byte[] bts = new byte[2];
            foreach (Match m in mc)
            {
                bts[0] = (byte)int.Parse(m.Groups[2].Value, NumberStyles.HexNumber);
                bts[1] = (byte)int.Parse(m.Groups[1].Value, NumberStyles.HexNumber);
                r += Encoding.Unicode.GetString(bts);
            }
            return r;
        }