using System;

using System.Text.RegularExpressions;

using System.Web;

​

public class Program

{

    public static void Main()

    {

        string external_url = "https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.runnerfiore.com%2FProduct%2FSocial-Skills-Lessons-for-Empathy-and-Perspective-Taking-SEL-Activities-3616246%3Ffbclid%3DIwZXh0bgNhZW0CMTAAAR1FZGD3nplG4HwPfWkDQGBrevjzPAA5-UPxjRyyV5rK03CxmejaGVvnv2w_aem_RHm2MsAthrIzwvCZADdamQ&h=AT32U7yxfji0rtuz1iRL7j5jpYARvIKFCJ21l86lZ7ppgZ0OG4fFK58FHPnkUCDXRXzJb_8v1j-tUiks1fMe3njtBOsZWegsemOubQfznPvWRBH23zOt1u7_yPEsW3IjCz0S6Q";

        // Buscar el URL codificado

        var match = Regex.Match(external_url, @"(?<=facebook\.com.*?php\?u=)(http.*?)(?=&)");

        if (match.Success)

        {

            // Decodificar el URL para hacerlo legible

            string decodedUrl = HttpUtility.UrlDecode(match.Value);

            Console.WriteLine(decodedUrl); // Imprimir el resultado en la consola

        }

        else

        {

            Console.WriteLine("No se encontró un URL válido."); // Mensaje en caso de fallo

        }

    }

}

​

​