Get only the prefix from a host name in a given URL

Question

I need to get the domain name without the top level domain suffix of a given url.

e.g

• Url :www.google.com then output=google

• Url :http://www.google.co.uk/path1/path2 then output=google

• Url :http://google.co.uk/path1/path2 then output=google

• Url :http://google.com then output=google

• Url :http://google.co.in then output=google

• Url :http://mail.google.co.in then output=google

For that i try this code

 var uri = new Uri("http://www.google.co.uk/path1/path2");
 var sURL = uri.Host;
 string[] aa = sURL.Split('.');
 MessageBox.Show(aa[1]);

But every time i can't get correct output(specialty url without www). after that i search no google and try to solve it but it's help less. i also see the question on stackoverflow but it can't work for me.

Answer 1

This answer is just for completeness, cause I think it would be a valid approach, if it wouldn't be so complicated and essentially abuse the DNS system. Note that this isn't 100% foolproof either (and requires access to a DNS).

• Extract the full domain name of the URL. Let's take http://somepart.subdomain.example.org/some/files as an example. We'd get somepart.subdomain.example.org.
• Split the domain name at dots: {"somepart", "subdomain", "example", "org"}.
• Take the rightmost part (org) and see whether it is a known (top level) domain name.
  • If it is, the next part to the left is the domain name you're looking for.
  • If it isn't, try to retrieve an IP for this.
  • If there's an IP for it, the last added part is your domain name.
  • If there isn't an IP either, add the next part to the left and repeat these checks (in this example you'd now test for example.org).

Answer 2

The right answer to your question is: No you can't.

The only solution that can almost achieve it in a dirty and not easy to maintain way is to have a list with all the existent TopLevelDomain (you can find an incomplete one in this SO answer)

var allTld = new[] {".com", ".it",".co.uk"}; //there you have find a really big list of all TLD
string urlToCheck = "www.google.com";//sports-ak.espn.go.com/nfl/  http://www.google.co.uk/path1/path2
if (!urlToCheck.StartsWith("http", StringComparison.OrdinalIgnoreCase))
{
    urlToCheck = string.Concat("http://", urlToCheck);
}
var uri = new Uri(urlToCheck);

string domain = string.Empty;
for (int i = 0; i < allTld.Length; i++)
{
    var index = uri.Host.LastIndexOf(allTld[i], StringComparison.OrdinalIgnoreCase);
    if (index>-1)
    {
        domain = uri.Host.Substring(0, index);
        index = domain.LastIndexOf(".", StringComparison.Ordinal);
        if (index>-1)
        {
            domain = domain.Substring(index + 1);break;
        }
    }
}
if (string.IsNullOrEmpty(domain))
{
    throw new Exception(string.Format("TLD of url {0} is missing", urlToCheck));
}

IMHO You should ask yourself: Do I really need the name without the TLD?

Answer 3

This is the best you can get. It's not a maintainable solution, it is not a "fast" solution. (GetDomain.GetDomainFromUrl should be optimized).

• Use GetDomain.GetDomainFromUrl
• In TldPatterns.EXACT add "co.uk" (I don't know why it doesn't exist in the first place)
• Some other minor string manipulations

This what it should look like:

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

        class TldPatterns
        {
            private TldPatterns()
            {
                // Prevent instantiation.
            }

            /**
             * If a hostname is contained in this set, it is a TLD.
             */
            static public string[] EXACT = new string[] {
             "gov.uk",
             "mil.uk",
             "co.uk",
             //...

    public class Program
    {

        static void Main(string[] args)
        {
            string[] urls = new[] {"www.google.com", "http://www.google.co.uk/path1/path2 ", "http://google.co.uk/path1/path2 ",
            "http://google.com", "http://google.co.in"};
            foreach (var item in urls)
            {
                string url = item;
                if (!Regex.IsMatch(item, "^\\w+://"))
                    url = "http://" + item;
                var domain = GetDomain.GetDomainFromUrl(url);
                Console.WriteLine("Original    : " + item);
                Console.WriteLine("URL         : " + url);
                Console.WriteLine("Domain      : " + domain);
                Console.WriteLine("Domain Part : " + domain.Substring(0, domain.IndexOf('.')));
                Console.WriteLine();
            }
        }
    }

Outputs:

Original    : www.google.com
URL         : http://www.google.com
Domain      : google.com
Domain Part : google

Original    : http://www.google.co.uk/path1/path2
URL         : http://www.google.co.uk/path1/path2
Domain      : google.co.uk
Domain Part : google

Original    : http://google.co.uk/path1/path2
URL         : http://google.co.uk/path1/path2
Domain      : google.co.uk
Domain Part : google

Original    : http://google.com
URL         : http://google.com
Domain      : google.com
Domain Part : google

Original    : http://google.co.in
URL         : http://google.co.in
Domain      : google.co.in
Domain Part : google

Answer 4

I have tested using following Regex with your all cases and it works.

string url = "http://www.google.co.uk/path1/path2";
Regex rgx = new Regex(@"(http(s?)://)?(www.)?((?<content>.*?)\.){1}([\w]+\.?)+");
Match MatchResult = rgx.Match(url);
string result = MatchResult.Groups["content"].Value; //google