TabbedBrowserForm.cs

using System;
using System.Windows.Forms;
using CefSharp;
using CefSharp.WinForms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        private TabControl _tabControl = null;

        public Form1()
        {
            InitializeComponent();

            if (!Cef.IsInitialized)
            {
                CefSettings settings = new CefSettings();

                // Register the "local" scheme
                settings.RegisterScheme(new CefCustomScheme
                {
                    SchemeName = "local",
                    SchemeHandlerFactory = new LocalSchemeHandlerFactory(),
                    IsSecure = true
                });

                Cef.Initialize(settings);
            }

            // Create the TabControl
            _tabControl = new TabControl
            {
                Dock = DockStyle.Fill
            };
            this.Controls.Add(_tabControl);

            // Add the default tabs
            this.AddNewTab("https://www.google.com");
            this.AddNewTab("https://www.w3schools.com/jsref/met_win_close.asp");    // Test window.open and window.close
            this.AddNewTab("http://www.thispagedoesnotexist.com");  // Test load error handling
        }

        public void AddNewTab(string url)
        {
            // Create a new browser
            ChromiumWebBrowser browser = new ChromiumWebBrowser(url)
            {
                Dock = DockStyle.Fill,
                LifeSpanHandler = new LifeSpanHandler(this),
                LoadHandler = new LoadHandler()
            };

            // Create a new tab
            TabPage tab = new TabPage(url);
            tab.Controls.Add(browser);

            // Add it to the tab control
            _tabControl.Controls.Add(tab);
        }

        public Control AddNewPopup(string url)
        {
            // Create a new host control
            Control host = new Control
            {
                Dock = DockStyle.Fill
            };

            // Create a new tab
            TabPage tab = new TabPage(url);
            tab.Controls.Add(host);

            _tabControl.Invoke(new Action(() =>
            {
                // Add it to the tab control
                _tabControl.Controls.Add(tab);
            }));

            return host;
        }

        public void CloseTab(TabPage tab)
        {
            _tabControl.Invoke(new Action(() =>
            {
                // Remove this tab
                _tabControl.Controls.Remove(tab);
            }));
        }
    }
}