using System;

public class Program

{

    public static void Main()

    {

        var myUri = new Uri("http://www.themine.com:8080/path/test.html");

        Console.WriteLine(myUri.AbsoluteUri);

        Console.WriteLine(myUri.AbsoluteUriWithoutPort());

    }

}

​

public static class UriExtensions {

​

    public static string AbsoluteUriWithoutPort(this System.Uri uri) {

        var url = new System.UriBuilder(uri);

        url.Port = -1;

        return url.Uri.ToString();

    }

}

​