Cant get HTML from cefsharp browser after selecting pagination

Question

1. Using cefsharp I loaded a page that gives 25 links in a page.
2. using FrameLoadEnd got HTML content into HtmlAgilityPack Document.
3. Got title from nodes for 25 links. Problem When i click for 50 links on page and try to get titles, it still gives me 25 links. which is old page. i could not figureout why FrameLoadEnd is not able to change the html when navigated to another link within page.

When I click 50 titles i cannot get the html content for 50 titles

here is code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using CefSharp;
using CefSharp.WinForms;
using System.Windows.Forms;
using HtmlAgilityPack;

namespace Hummingbird_HAP_E_Scraper
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            chromiumWebBrowser1.Load("https://www.sciencedirect.com/search?qs=nursing");
        }
        string html;
        private void ChromiumWebBrowser1_FrameLoadEnd(object sender, CefSharp.FrameLoadEndEventArgs e)
        {
            BeginInvoke((Action)(async () =>
            {
                html = await chromiumWebBrowser1.GetSourceAsync();
            }));
        }
       HtmlAgilityPack.HtmlDocument xdoc = new HtmlAgilityPack.HtmlDocument();
        private void Button1_Click(object sender, EventArgs e)
        {
            xdoc.LoadHtml(html);
            System.Threading.Thread.Sleep(5000);
          
            HtmlNodeCollection links;
            links = xdoc.DocumentNode.SelectNodes("//h2/span/a");
                    if (links == null)
                        return;
                    foreach (HtmlNode link in links)
                    {
                         listBox1.Items.Add(link.InnerText);
   
                    }
            }
    }
}