Using C# dll with Cefsharp in VB6 application

Question

I'm updating a program in vb6 calling a Winform C# dll through COM interop. In this C# dll, the winform contain a webbrowser that instantiate Internet Explorer (.NET default browser). For compatibility issues, I need to embed Chromium. I've decided to go with CefSharp.

I've set up a test project in C# calling this dll & it's working fine. I've read CefSharp Wiki and they precise to initialize/shutdown Cef from the main UI thread. So I declare two methods in C# that I call directly in VB6. Issue is: the form is loading fine and browser with CefSharp is running. When I close the form and want to launch it again, application just shuts down. I've also tried to intialize/shutdown CefSharp in the C# dll with no success.

Any idea on how to correctly use CefSharp in this case? Thanks

Public gTest as boolean
Option Explicit

Public Function LaunchDLL() As Boolean

Dim oExtApp: Set oExtApp = CreateObject("TestCefSharp.Class2")
Dim test As Boolean

Dim bResult     As Boolean

    LaunchDLL = False
    On Error GoTo Erreur

    If gTest = False Then
        oExtApp.InitializeChromium
        gTest = True
    End If
    LaunchDLL = oExtApp.LaunchingForm

    Set oExtApp = Nothing

    Exit Function

Erreur:
MsgBox Err.Description
End Function

Public Sub LaunchBrowser_Click()
Dim test As Boolean
Dim Chrome As Boolean

test = LaunchDLL()
End Sub

namespace TestCefSharp
{
    public interface IExternalApp
    {
        bool LaunchingForm();

        bool InitializeChromium();

        bool ShutdownChromium();
    }
    public abstract class CExternalApp : IExternalApp
    {

        public CExternalApp()
            : base()
        {

        }

        public bool LaunchingForm()
        {
            bool test = false;
            MessageBox.Show("Starting");
            Form1 form1 = new Form1();
            DialogResult result = form1.ShowDialog();
            if (result == DialogResult.OK)
            { test = true; }
            else
            { test = false; }
            return test ;
        }

        public bool InitializeChromium()
        {
            MessageBox.Show("Chromium initialized");
            bool result = false;
            try
            {
                CefSharpSettings.SubprocessExitIfParentProcessClosed = true;
                CefSharpSettings.ShutdownOnExit = false;
                Cef.EnableHighDPISupport();

                var settings = new CefSettings()
                { CachePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "CefSharp\\Cache")};

                Cef.Initialize(settings);
                result = true;
            }
            catch
            { }
            return result;
        }

        public bool ShutdownChromium()
        {
            MessageBox.Show("Chromium ended");
            bool result = false;
            try
            {
                Cef.Shutdown();
                result = true;
            }
            catch
            { }
            return result;
        }
    }
}

Answer 1

In fact, it's not working with the debug mode from VB6 editor... If I compile and launch directly the executable, all is working well.

I'll have to dig in a bit further but I think it comes from the fact that VB6 editor does not launch a separate thread in debug like VS2017 does in .NET.

Anyway, thanks for the help.