using System;

using System.Web;

public class Program

{

    public static void Main()

    {

        var text = "GuidePlayer_20201119_29.htm?Skin=infocaption5&Project=infocaption5&OfflinePlayer=true";

        var enc1 = HttpUtility.HtmlEncode(text);

        Console.WriteLine(enc1);

        var enc2 = HttpUtility.HtmlDecode(text);

        Console.WriteLine(enc2);

        var enc3 = HttpUtility.UrlEncode(text);

        Console.WriteLine(enc3);

        var enc4 = HttpUtility.UrlDecode(text);

        Console.WriteLine(enc4);

    }

}