using System;

using System.Web;

​

public class Program

{

    public static string GetParameterFromUrl(string url, string paramname)

    {

        return HttpUtility.ParseQueryString((new Uri(url)).Query).Get(paramname) ?? null;

    }

    public static void Main()

    {

        string Strings = "http://alianzas.qapaq.pe/PlataformaGestion/Gestion/?ref=Affiliate_AskRobin&VariableR=853199";

        Console.WriteLine(GetParameterFromUrl(Strings, "VariableR") ?? "No query parameter with that name");

    }

}