Exposed function not connecting or not firing properly

[mwpowellhtx]

Trying to connect a click event on an <a/> element.

I am positive the Context is good, and I debugged in and know I have a valid anchor element instance.

The expose function is not failing for any reason, and apparently the element event connection is being made.

But I get no callback occur back into my code for whatever reason.

First, I gather I need to maintain the context instance; I am. And maintain that instance until the next Browser address change, at which point I dispose of the old one, which I presume is also like clearing the exposed functions cache, and generate a new context on the new page. I rinse and repeat the whole process, connecting the function, etc.

private void OnLogoutClick()
{
    // TODO: respond to logout
}

protected virtual async Task<bool> TryVerifyLogoutAsync(ChromiumWebBrowser browser)
{
    var context = Context;
    Debug.Assert(context is not null, $"{nameof(context)} expected, was null.");

    if (!browser.Address.Equals(LoginUrl, InvariantCultureIgnoreCase))
    {
        var aLogout = await Context.QuerySelectorAsync<HtmlAnchorElement>(S.Logout);
        await Context.ExposeFunctionAsync("onLogoutClick", OnLogoutClick);
        await aLogout.AddEventListenerAsync("click", "onLogoutClick");
        return true;
    }

    return false;
}

I'm assuming it is "click" at least according to this documentation, but maybe I am missing something there. Or perhaps I also need to maintain the anchor element instance once I have obtained that as well, which would be understandable, in addition to its context.

[mwpowellhtx]

What I am wondering is, do I need to arrange CefSettings or other Chromium flags to allow for things such. I started more than less in this minimal example just to get some things on their feet, and for the most part, it's fantastic, it works quite well. Except apparently in a couple of areas, maybe I need to configure a bit differently.

[mwpowellhtx]

Perhaps needing some degree of multithreading enabled and configured as well to allow for async callbacks? I forget exactly where I found that snippet, probably among the same minimal examples.

var settings = new CefSettings();
settings.MultiThreadedMessageLoop = false; // This defaults to true

Cef.Initialize(settings);

// -For WPF use[DispatcherTimer](https://docs.microsoft.com/en-us/dotnet/api/system.windows.threading.dispatchertimer?view=netframework-4.8)
// -For WinForms use[Timer](https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.timer?view=netframework-4.8)

// Set the timer Interval to 30 times per second, can be increased to 60 if required
// For WPF
timer.Interval = TimeSpan.FromMilliseconds(1000 / 30);
// For WinForms
timer.Interval = 1000 / 30;
timer.Tick += UiThreadTimerTick;
timer.Start();

// Before closing your app
// Calling Cef.DoMessageLoopWork() after Cef.Shutdown has been called will result in an access violation, make sure you stop you timer first.
timer.Tick -= UiThreadTimerTick;
timer.Stop();

[amaitland]

First, I gather I need to maintain the context instance; I am. And maintain that instance until the next Browser address change, at which point I dispose of the old one, which I presume is also like clearing the exposed functions cache, and generate a new context on the new page

The expected usage is a single DevToolsContext per browser instance. Use the same instance until the browser is disposed. Functions should persist even after navigations.

The scenario you've described is not one that I've ever tested. This is not the standard use case for Puppeteer.

[mwpowellhtx]

I see, one instance per browser instance. So, ostensibly, I should rather position such a thing as a UserControl.Resource, let's say,, if that is where I am hosting the browser instance?

Yes, I have generally been keeping one context per function or method body, not as you described...