using System;

using System.Net;

public class Program

{

    public static void Main()

    {

        string a = WebUtility.HtmlEncode("Adidas<sub>®</sub>");

        string b = a.ToHtmlDecode();

​

        Console.WriteLine("After HtmlEncode: " + a);

        Console.WriteLine("After HtmlDecode: " + b);

    }

}

​

public static class StringHelper

{

    public static string ToHtmlDecode(this string encoded)

    {

        return WebUtility.HtmlDecode(encoded);

    }

}