using System;

public class Program

{

    public static void Main()

    {

        var baseUrl = "https://some.base.url/somefolder/somepage";

        var pageUrl = "other/page";

        var baseUri = new Uri(baseUrl);

        var uri = new Uri(baseUri, pageUrl);

        Console.WriteLine(baseUri.AbsoluteUri);     

        Console.WriteLine(baseUri + pageUrl);                   

    }

}