using System;

using System.Web;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        // URL examples from: https://mathiasbynens.be/demo/url-regex

        List<string> shouldPass = new List<string>() { 

            "http://foo.com/blah_blah",

"http://foo.com/blah_blah/",

"http://foo.com/blah_blah_(wikipedia)",

"http://foo.com/blah_blah_(wikipedia)_(again)",

"http://www.example.com/wpstyle/?p=364",

"https://www.example.com/foo/?bar=baz&inga=42&quux",

"http://✪df.ws/123",

"http://userid:password@example.com:8080",

"http://userid:password@example.com:8080/",

"http://userid@example.com",

"http://userid@example.com/",

"http://userid@example.com:8080",

"http://userid@example.com:8080/",

"http://userid:password@example.com",

"http://userid:password@example.com/",

"http://142.42.1.1/",

"http://142.42.1.1:8080/",

"http://➡.ws/䨹",

"http://⌘.ws",

"http://⌘.ws/",

"http://foo.com/blah_(wikipedia)#cite-1",

"http://foo.com/blah_(wikipedia)_blah#cite-1",

"http://foo.com/unicode_(✪)_in_parens",

"http://foo.com/(something)?after=parens",

"http://☺.damowmow.com/",

"http://code.google.com/events/#&product=browser",

"http://j.mp",

"ftp://foo.bar/baz",

"http://foo.bar/?q=Test%20URL-encoded%20stuff",

"http://مثال.إختبار",

"http://例子.测试",

"http://उदाहरण.परीक्षा",

"http://-.~_!$&'()*+,;=:%40:80%2f::::::@example.com",

"http://1337.net",

"http://a.b-c.de",

"http://223.255.255.254"

        };

        List<string> customParserResult = new List<string>();

        foreach(string s in shouldPass) {

            char[] buffer = new char[s.Length];

            for(int i = 0; i < s.Length; i++){

                char c = s[i];

                if(

                    (c >= '0' && c <= '9') ||

                    (c >= 'A' && c <= 'Z') ||

                    (c >= 'a' && c <= 'z') ||

                    (c == '_') ||

                    (c == '-')

                  )

                {

                    buffer[i] = c;

                }

            }

            customParserResult.Add(new string(buffer));

        }

        for(int i = 0; i < customParserResult.Count; i++){

            string customParsed = customParserResult[i];

            string original = shouldPass[i];

            Console.WriteLine("Original: " + original);

            Console.WriteLine("Encoded: " + HttpUtility.UrlEncode(original));

            Console.WriteLine("Decoded: " + HttpUtility.UrlDecode(HttpUtility.UrlEncode(original)));

            Console.WriteLine("Custom: " + customParsed);

            Console.WriteLine("\n\n");

        }

    }

}