EvaluateScriptAsync hanging

Question

In CefSharp WinForms, I'm trying to get the html source of the page using JS once the page has loaded, however the application is freezing. I'm using a BackgroundWorker and the concerned functions are as follows:

void bw_DoWork(object sender, DoWorkEventArgs e)
{
    browser.Load("http://www.google.com");

    browser.FrameLoadEnd += delegate
    {
        object js = EvaluateScript(browser, "1+1");
        MessageBox.Show(js.ToString());
    };
}

object EvaluateScript(ChromiumWebBrowser b, string script)
{
    var task = b.EvaluateScriptAsync(script);
    task.Wait();
    return task.Result;
}

Answer 1

As amaitland pointed out, FrameLoadEnd was causing the hang by running in the UI thread. The below code is working:

void bw_DoWork(object sender, DoWorkEventArgs e)
{
    first.Load("http://www.google.com");

    browser.FrameLoadEnd += delegate
    {
        Task task = new Task(() => {
            object js = EvaluateScript(browser, "document.getElementsByTagName('html')[0].innerHTML;");
            MessageBox.Show(js.ToString());
        });
        task.Start();
    };
}

static object EvaluateScript(ChromiumWebBrowser b, string script)
{
    var task = b.EvaluateScriptAsync(script);
    task.Wait();
    JavascriptResponse response = task.Result;
    return response.Success ? (response.Result ?? "") : response.Message;
}

Answer 2

Whilst you assign FrameLoadEnd in the BackgroundWorker thread, it's actually executed on the underlying CEF UI thread, for which you cannot block without issues.

I'd typically suggest you spawn a Task from within the event handler to complete your work.