using System;

using System.Linq;

public class Program

{

        public static void Main(string[] args)

        {

            var path = "https://some-test-url.com:443";

            var qs = new string(path.SkipWhile(c => c != '?')

                           .Skip(1)

                           .TakeWhile(c => c != '#')

                           .ToArray()).Trim();

            Console.WriteLine(qs);

            Console.WriteLine(string.IsNullOrWhiteSpace(qs));

        }

}