using System;

using HtmlAgilityPack;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using Fizzler.Systems.HtmlAgilityPack;

public class Program

{

    public class Item {

        public string Title { get; set; }

        public string Text { get; set; }

    }

    public static void Main()

    {       

        var doc = new HtmlDocument();

        var html = "<p><b>Test1</b></p><p>Test21 paragraph</p><p><b>Test2</b></p><p>Test2 paragraph</p><p><b>Test3</b></p><p>Test3 paragraph</p>";      

        var str = "";

        doc.LoadHtml(html);

        IEnumerable nodes = doc.DocumentNode.QuerySelectorAll("p");

        var items = new List<Item>();

        var item = new Item();

        foreach (HtmlNode node in nodes)

        {                       

            if (node.SelectSingleNode("./b") is not null) {                         

               item = new Item();

               item.Title = node.SelectSingleNode("./b").InnerText;              

            }

            else {                             

                item.Text = node.InnerText.Trim();

                items.Add(item);

            }

        }

        foreach(var i in items) {

            Console.WriteLine(i.Title + "\n" + i.Text + "\n\n");

        }

        Console.WriteLine(str);         

    }

}