EvaluateScriptAsync for SelfContained application

[Zelya]

Is there an existing issue for this?

• I have searched both open/closed issues, no issue already exists.

CefSharp Version

121.3.70

Operating System

Windows 11

Architecture

x64

.Net Version

NET 8.0

Implementation

WPF

Reproduction Steps

1. Add EvaluateScriptAsync code to your project, like this

        private async void Browser_LoadingStateChanged(object? sender, CefSharp.LoadingStateChangedEventArgs e)
        {
            string script = @"document.querySelector('someelement')";

            var response = await Browser.GetFocusedFrame().EvaluateScriptAsync(script, null);

            if (response.Success)
            {

It works OK.
2. In order to make browser working with SelfContained=true (see #3407) add code sninppet from MinimalExample https://github.com/cefsharp/CefSharp.MinimalExample/blob/master/CefSharp.MinimalExample.Wpf/Program.PublishSingleFile.cs
This is the most valuable part.

            var settings = new CefSettings()
            {
                CachePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "CefSharp\\Cache"),
                BrowserSubprocessPath = System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName
            };

            Cef.Initialize(settings, performDependencyCheck: false);

3. Now EvaluateScriptAsync hangs forever.

Expected behavior

EvaluateScriptAsync should work for app with SelfContained=true

Actual behavior

EvaluateScriptAsync hangs for app with SelfContained=true and workaround from MinimalExample

Regression?

No response

Known Workarounds

No response

Does this problem also occur in the CEF Sample Application

Not Tested

Other information

No response

[amaitland]

Follow the instructions at https://github.com/cefsharp/CefSharp/wiki/SelfHost-BrowserSubProcess

Make sure to change the stack size of your application.

private async void Browser_LoadingStateChanged(object? sender, CefSharp.LoadingStateChangedEventArgs e)
{
string script = @"document.querySelector('someelement')";

        var response = await Browser.GetFocusedFrame().EvaluateScriptAsync(script, null);

        if (response.Success)
        {

There are two problems with this code block

1. You aren't checking if the browser is actually loaded. e.g. LoadingStateChangedEventArgs.IsLoading
2. Returning DOM elements directly is not supported.

You cannot directly return a DOM Element (or anything with a cyclic reference), you need to create a new object that has just the information you need to return.

As per https://github.com/cefsharp/CefSharp/wiki/General-Usage#2-how-do-you-call-a-javascript-method-that-returns-a-result

For simple elements it might work with an 8mb stack size. It's likely crashing the render process in your case.

See https://github.com/cefsharp/CefSharp.Dom for an alternative DOM API.

[Zelya]

@amaitland

You aren't checking if the browser is actually loaded. e.g. LoadingStateChangedEventArgs.IsLoading

Sorry, skipped this for smaller code snippet. But this doesn't help.

Returning DOM elements directly is not supported.

The same. Code like string script = @"document.querySelector('someelement').value;" doesn't work too.

See https://github.com/cefsharp/CefSharp.Dom for an alternative DOM API.

Tried, but it hangs on await chromiumWebBrowser.CreateDevToolsContextAsync();

Without SelfHost BrowserSubProcess everything works good.

[amaitland]

Quick test with https://github.com/cefsharp/CefSharp.MinimalExample changing the netcore WPF Example to SelfContained and targeting .Net 6.0. EvaluateScriptAsync is working as expected

I'd suggest testing with the MinimalExample and seeing how it behaves. For SelfContained builds that target net6.0-windows it will default to self hosting.

Follow the instructions at https://github.com/cefsharp/CefSharp/wiki/SelfHost-BrowserSubProcess

Make sure you double check you've implemented everything as per the guide. This is more up to date than the issue you linked.