public static string UrlDecode(string input)
 {
     var arr = input.Split(new[] {'%'}, StringSplitOptions.RemoveEmptyEntries);
     var bytes = arr.Select(s => Convert.ToByte(s, 16)).ToArray();
     var result = Encoding.GetEncoding("GB2312").GetString(bytes, 0, bytes.Length);
     return result;
 }