using System;

using System.Web;

using System.Net;

public class Program

{

    public static void Main()

    {

        string a = "%5B%7B%22Details";

        string b = HttpUtility.HtmlEncode(a);       

        Console.WriteLine(b);

        b = WebUtility.HtmlEncode(a);       

        Console.WriteLine(b);

        b = Uri.UnescapeDataString(a);

        Console.WriteLine(b);

    }

}