CefSharp Offscreen example as a dynamic library called by WinForm application

Question

I wrote a shared library which consumes CefSharp.Offscreen to do the html retrieving work. It works fine when a Console Application calls it. But when a WinForm app connects it, after tcs.TrySetResult(true) is executed, it does not jump into await browser.GetSourceAsync() as what it did in Console App.

In WinForm App, it could be successful if any UI element is not created and not in the UI constructor, but if I create a UI element before calling the shared library, it fails always.

In another way, I force calling "var source = await browser.GetSourceAsync();" to get current html source, but it still does not response in WinForm connection.

        [STAThread]
        static void Main()
        {
            // I can put the init code here, but it does not help
            //CefSimpleLib.CefTest.Initialize();

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            TextBox tb = new TextBox(); // this blocks below call
            CefSimpleLib.CefTest cf = new CefSimpleLib.CefTest();

            Application.Run(new FormMain());
            //CefSimpleLib.CefTest.UnInitialize();
        }


namespace CefSimpleLib
{
    public class CefTest
    {
        public CefTest()
        {
            // You need to replace this with your own call to Cef.Initialize();
            // Default is to use an InMemory cache, set CachePath to persist cache

            Cef.Initialize(new CefSettings { CachePath = "cache" });

            MainAsync();

            System.Threading.Thread.Sleep(1000 * 1000);

            Cef.Shutdown();

        }

        private async void MainAsync()
        {
            var browserSettings = new BrowserSettings();
            //Reduce rendering speed to one frame per second, tweak this to whatever suites you best
            browserSettings.WindowlessFrameRate = 1;

            using (var browser = new ChromiumWebBrowser("https://www.baidu.com", browserSettings))
            {
                await LoadPageAsync(browser);
                var source = await browser.GetSourceAsync();


                await Task.Delay(10);
            }
        }

        public Task LoadPageAsync(IWebBrowser browser)
        {
            var tcs = new TaskCompletionSource<bool>();

            EventHandler<LoadingStateChangedEventArgs> handler = null;
            handler = (sender, args) =>
            {
                //Wait for while page to finish loading not just the first frame
                if (!args.IsLoading)
                {
                    browser.LoadingStateChanged -= handler;
                    tcs.TrySetResult(true);
                }
            };

            browser.LoadingStateChanged += handler;

            return tcs.Task;
        }
    }
}