EvaluateScriptAsync won't return second time

[zangetsudo]

Is there an existing issue for this?

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

CefSharp Version

138.0.170

Operating System

Windows 10

Architecture

x64

.Net Version

net fwk 4.7.2

Implementation

OffScreen

Reproduction Steps

run it every time

Expected behavior

run as normal

Actual behavior

run it every time, it will blocked and won't return.
(
code: await Task.WhenAll(tcs.Task);
function : InjectScriptAndRun
)

Regression?

dont konw if it works before.

Known Workarounds

No response

Does this problem also occur in the CEF Sample Application

Yes using WPF/OffScreen command line args

Other information

    public static void LoadPageAsync(ChromiumWebBrowser browser)
    {
        var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
        EventHandler<LoadingStateChangedEventArgs> handler = null;
        handler = (sender, args) =>
        {
            if (!args.IsLoading)
            {
                browser.LoadingStateChanged -= handler;                    
                tcs.TrySetResult(true);
            }
        };
        browser.LoadingStateChanged += handler;
        var r = Task.WhenAll(tcs.Task);
        r.Wait();
    }

    private static async Task InjectScriptAndRun(ChromiumWebBrowser browser, string js, string shotName)
    {
        var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
        EventHandler<LoadingStateChangedEventArgs> handler = null;
        handler = (s, e) =>
        {
            if (!e.IsLoading)
            {
                Thread.Sleep(500);
                var scriptTask = browser.EvaluateScriptAsync(js);                    
                scriptTask.ContinueWith(t =>
                {
                    if (!t.Result.Success)
                    {
                        tcs.TrySetException(new Exception("EvaluateScriptAsync failed:" + t.Result.Message));                            
                    }
                    else
                    {
                        Thread.Sleep(500);
                        var task = browser.CaptureScreenshotAsync();
                        task.ContinueWith(x =>
                        {
                            var screenshotPath = Path.Combine(myPath, $"CefSharp screenshot {shotName}.png");
                            var bitmapAsByteArray = x.Result;
                            File.WriteAllBytes(screenshotPath, bitmapAsByteArray);
                            Process.Start(new ProcessStartInfo(screenshotPath)
                            {
                                UseShellExecute = true
                            });
                        }, TaskScheduler.Default);
                        tcs.TrySetResult(true);
                    }
                    browser.LoadingStateChanged -= handler;
                });

            }
        };
        browser.LoadingStateChanged += handler;
        await Task.WhenAll(tcs.Task);
    }
    
    
    main:
    

      const string testUrl = "https://aaa.com";
      const string issueUrl = "https://bbb.com";
      
      var settings = new CefSettings()
      {
          CachePath = Path.Combine(myPath, "CefSharp")
      };

      Cef.Initialize(settings, performDependencyCheck: true, browserProcessHandler: null);
      var browser = new ChromiumWebBrowser(testUrl);

      var t1 = InjectScriptAndRun(browser, js, "login");
      Task.WaitAll(t1);

      browser.LoadUrl(issueUrl);
      LoadPageAsync(browser);

      Thread.Sleep(500);
      var t2 = InjectScriptAndRun(browser, ei, "issue");

      Task.WaitAll(t2);

[zangetsudo]

it's ok the first time:
var t1 = InjectScriptAndRun(browser, js, "login");
but be blocked the second time:
var t2 = InjectScriptAndRun(browser, ei, "issue");

[amaitland]

The API is asynchronous, using it in a synchronous fashion is not recommended or supported.

If you are using CefSharp.OffScreen in a console application then there is an example at https://github.com/cefsharp/CefSharp.MinimalExample/blob/master/CefSharp.MinimalExample.OffScreen/Program.cs#L48 which you can adapt to your needs.

There are a number of built in methods that you should also use instead of writing your own.
https://github.com/cefsharp/CefSharp/blob/master/CefSharp.Test/OffScreen/WaitForRenderIdleTests.cs#L33
https://github.com/cefsharp/CefSharp/blob/master/CefSharp.Test/Navigation/WaitForNavigationAsyncTests.cs#L36

CefSharp/CefSharp.Test/OffScreen/OffScreenBrowserTests.cs

Line 52 in 56d048c

var response = await browser.LoadUrlAsync("www.google.com");

[amaitland]

If all you need is a headless browser then you should also consider switching to https://github.com/hardkoded/puppeteer-sharp