Это больше того, что вы ищете?
string input = @"such as () and § untouched.";
//Console.WriteLine(input);
Console.WriteLine(HttpUtility.UrlEncodeUnicode(input));
Console.WriteLine(HttpUtility.UrlEncode(input));
string everything = string.Join("", input.ToCharArray().Select(c => "%" + ((int)c).ToString("x2")).ToArray());
Console.WriteLine(everything);
Console.WriteLine(HttpUtility.UrlDecode(everything));
//This is my understanding of what you're asking for:
string everythingU = string.Join("", input.ToCharArray().Select(c => "%u" + ((int)c).ToString("x4")).ToArray());
Console.WriteLine(everythingU);
Console.WriteLine(HttpUtility.UrlDecode(everythingU));
который выводит:
such+as+()+and+%u00a7+untouched.
such+as+()+and+%c2%a7+untouched.
%73%75%63%68%20%61%73%20%28%29%20%61%6e%64%20%a7%20%75%6e%74%6f%75%63%68%65%64%2e
such as () and � untouched.
%u0073%u0075%u0063%u0068%u0020%u0061%u0073%u0020%u0028%u0029%u0020%u0061%u006e%u0064%u0020%u00a7%u0020%u0075%u006e%u0074%u006f%u0075%u0063%u0068%u0065%u0064%u002e
such as () and § untouched.