using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(IsDomainValid("example.com"));

        Console.WriteLine(IsDomainValid("try.direct"));

        Console.WriteLine(IsDomainValid("my-example.com"));

        Console.WriteLine(IsDomainValid("subdomain.example.com"));

        Console.WriteLine(IsDomainValid("example.com"));

        Console.WriteLine(IsDomainValid("example23.com"));

        Console.WriteLine(IsDomainValid("regexp-1222.org"));

        Console.WriteLine(IsDomainValid("read-book.net"));

        Console.WriteLine(IsDomainValid("org.host.org"));

        Console.WriteLine(IsDomainValid("org.host.org"));

        Console.WriteLine(IsDomainValid("velmart.shop-products.md"));

        Console.WriteLine(IsDomainValid("ip2email.terronosp-222.lb"));

        Console.WriteLine(IsDomainValid("stack.com"));

        Console.WriteLine(IsDomainValid("sta-ck.com"));

        Console.WriteLine(IsDomainValid("sta---ck.com"));

        Console.WriteLine(IsDomainValid("9sta--ck.com"));

        Console.WriteLine(IsDomainValid("sta--ck9.com"));

        Console.WriteLine(IsDomainValid("stack99.com"));

        Console.WriteLine(IsDomainValid("99stack.com"));

        Console.WriteLine(IsDomainValid("sta99ck.com"));

        Console.WriteLine(IsDomainValid("sub.do.com"));

        Console.WriteLine(IsDomainValid("ss.sss-ss.ss"));

        Console.WriteLine(IsDomainValid("s.sss-ss.ss"));

        Console.WriteLine(IsDomainValid("s.s-s.ss"));

        Console.WriteLine(IsDomainValid("test.t.te"));

        Console.WriteLine();

        Console.WriteLine("INVALID TESTS");

        Console.WriteLine();

        Console.WriteLine(IsDomainValid("@example.ru:?"));

        Console.WriteLine(IsDomainValid("example22:89"));

        Console.WriteLine(IsDomainValid("@jefe@dd.ru@22-"));

        Console.WriteLine(IsDomainValid("example.net?1222"));

        Console.WriteLine(IsDomainValid("example.com:8080:"));

        Console.WriteLine(IsDomainValid(".example.com:8080:"));

        Console.WriteLine(IsDomainValid("---test.com"));

        Console.WriteLine(IsDomainValid("$dollars$.gb"));

        Console.WriteLine(IsDomainValid("sell-.me"));

        Console.WriteLine(IsDomainValid("open22.the-door@koll.ru"));

        Console.WriteLine(IsDomainValid("mem-.wer().or%:222"));

        Console.WriteLine(IsDomainValid("pop().addjocker.lon"));

        Console.WriteLine(IsDomainValid("regular-l=.heroes?"));

        Console.WriteLine(IsDomainValid(" ecmas cript-8.org "));

        Console.WriteLine(IsDomainValid("example.com::%"));

        Console.WriteLine(IsDomainValid("example:8080"));

        Console.WriteLine(IsDomainValid("example"));

        Console.WriteLine(IsDomainValid("examaple.com:*"));

        Console.WriteLine(IsDomainValid("-test.test.com"));

        Console.WriteLine(IsDomainValid("-test.com"));

        Console.WriteLine(IsDomainValid("dd-.test.com"));

        Console.WriteLine(IsDomainValid("dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd-.test.com"));

        Console.WriteLine(IsDomainValid("d-.test.com"));

    }

​

    private static bool IsDomainValid(string DomainName)

    {

        if (DomainName.Split('.').Length <= 1) return false;

        if (DomainName[0] == '.' || DomainName[DomainName.Length - 1] == '.') return false;

        if (DomainName[0] == '-' || DomainName[DomainName.Length - 1] == '-') return false;

        if (DomainName.Split('.')[0] == "-" || DomainName.Split('.')[0][DomainName.Split('.')[0].Length - 1] == '-') return false;

        if (Regex.IsMatch(DomainName, "[\\.]{2}")) return false;

        if (Uri.CheckHostName(DomainName) == UriHostNameType.IPv4) return false;

        if (!Regex.IsMatch(DomainName, "^[a-zA-Z_0-9.-]+$")) return false;

        return true;

    }

}