using System;

using System.Linq;

using System.Diagnostics;

​

public class Program

{

        public static void Main()

        {

            string[] allowedHosts =

            {

                "google.com",

                "yahoo.com",

                "espn.com"

            };

​

            // All true

            Debug.Assert(

                IsAllowed("google.com", allowedHosts) &&

                IsAllowed("google.com/bar", allowedHosts) &&

                IsAllowed("http://google.com/", allowedHosts) &&

                IsAllowed("http://google.com/foo/bar", allowedHosts) &&

                IsAllowed("http://google.com/foo/page.html?bar=baz", allowedHosts)

            );

​

            // All false

            Debug.Assert(

                !IsAllowed("foo.com", allowedHosts) &&

                !IsAllowed("foo.com/bar", allowedHosts) &&

                !IsAllowed("http://foo.com/", allowedHosts) &&

                !IsAllowed("http://foo.com/foo/bar", allowedHosts) &&

                !IsAllowed("http://foo.com/foo/page.html?bar=baz", allowedHosts)

            );

        }

        static bool IsAllowed(string uri, string[] allowedHosts)

        {

            UriBuilder builder = new UriBuilder(uri);

            return allowedHosts.Contains(builder.Host, StringComparer.OrdinalIgnoreCase);

        }

}

​