.Net 8 upgrade is not able send WM_DESTROY message to ActiveXControl from interop assembly

[Sachin-NI]

.NET version

net8.0-windows

Did it work in .NET Framework?

Yes

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Issue description

Parent container control is not sending WM_DESTROY message to the child control while disposing the ActiveX child controls and thus our custom onDestroy method never get called.

From my call stack, I could pin point the cause of this issue to be this change by @JeremyKuhne in DetachAndForward Method in AxHost.cs.
The issue is that isHandleCreated need to be stored before calling DetachWindow() method in the DetachAndForward method as we were doing earlier, because isHandleCreated value will always get set to false after calling DetachWindow method so the code inside the if block will never be executed in any case.

New Code after the changes done in this PR:

// New Code
private unsafe void DetachAndForward(ref Message m)
{
    DetachWindow();
    if (IsHandleCreated)
    {
        void* wndProc = (void*)PInvoke.GetWindowLong(this, WINDOW_LONG_PTR_INDEX.GWL_WNDPROC);
        m.ResultInternal = PInvoke.CallWindowProc(
            (delegate* unmanaged[Stdcall]<HWND, uint, WPARAM, LPARAM, LRESULT>)wndProc,
            HWND,
            (uint)m.Msg,
            m.WParamInternal,
            m.LParamInternal);

        GC.KeepAlive(this);
    }
}

Old Code before this PR:

// Old Code
private HWND GetHandleNoCreate() => IsHandleCreated ? (HWND)Handle : default;
private void DetachAndForward(ref Message m)
{
    IntPtr handle = GetHandleNoCreate();
    DetachWindow();
    if (handle != IntPtr.Zero)
    {
        IntPtr wndProc = User32.GetWindowLong(new HandleRef(this, handle), User32.GWL.WNDPROC);
        m.Result = User32.CallWindowProcW(wndProc, handle, (User32.WM)m.Msg, m.WParam, m.LParam);
    }
}

As we are going to release our product with .net 8, We need the fix to be also present in .net 8.

Steps to reproduce

• Go thorough this comment to reproduce this issue.

OR

1. Create a Parent Container Control:

   • Implement a parent container control that hosts ActiveX child controls.
   • Ensure the parent control has the necessary logic to create and manage the lifecycle of the child controls.

2. Add ActiveX Child Controls:

   • Add one or more ActiveX child controls to the parent container.
   • Ensure these child controls have custom OnDestroy methods that should be called when they are destroyed.

3. Implement Custom OnDestroy Method:

   • In the ActiveX child controls, implement a custom OnDestroy method that performs specific cleanup tasks.
   • Ensure this method is mapped to the WM_DESTROY message using the MESSAGE_HANDLER macro.

4. Trigger Disposal of Child Controls:

   • Implement a mechanism in the parent container to dispose of the child controls. This could be triggered by a user action or a specific event in the application.

5. Observe Message Handling:

   • Use debugging tools or logging to observe the messages sent to the child controls during the disposal process.
   • Specifically, check if the WM_DESTROY message is being sent to the child controls.

6. Verify OnDestroy Method Execution:

   • Verify whether the custom OnDestroy method in the child controls is being called.

[lonitra]

Reopening for pending work to add test + servicing

[Sachin-NI]

@lonitra / @JeremyKuhne , do you have an expected date for patching .NET 8.0 with this change? We urgently need this fix in .NET 8, as our product release depends on it and this issue is affecting our product quality.

[JeremyKuhne]

@Sachin-NI we need to get approval for it and validate the fix. If it is approved, it would be in February most likely.

[Syareel-Sukeri]

@Sachin-NI Could you provide a sample solution with the custom OnDestroy method in the child controls to verify its execution during disposal?

[Sachin-NI]

@Syareel-Sukeri,
I'm not able to attach the zip file in the comment hence I've uploaded it in my branch.
Download the zip file and you'll find 2 solution files in it. One is creating ActiveX COM control which also has WM_DESTROY msg handler and the other solution is importing that control in winForm and sending WM_DESTROY msg while disposing the form.
To reproduce the issue, first build (In Admin VS mode) NIComControl.sln and then build NIFormCOM.sln and launch the generated exe.
If OnDestroy method get called, then you would see "WM_DESTROY received" message pop-up. This is not happening currently, after this PR, this will be resolved.
Note: Make sure you build same configuration for both solutions.

[Tanya-Solyanik]

@LeafShi1 - please prepare backport PRs to release/8.0 and 9.0, when Syareel signs off on the fix, include both PRs attached to this issue. @JeremyKuhne will add tests to the servicing PRs later.

[Syareel-Sukeri]

@lonitra @Tanya-Solyanik There is an exception currently blocking the verification process when using binaries built from main branch of Winforms repo to verify. I will continue to verify again when all changes flow into SDK.

[lonitra]

@Syareel-Sukeri System.Private.Windows.GdiPlus is a new assembly added recently and should produce when building from main. Are you getting this exception if that dll is included?

[Syareel-Sukeri]

@lonitra Yes, I encounter the exception regardless of whether the System.Private.Windows.GdiPlus.dll is included.

[Syareel-Sukeri]

@lonitra @Tanya-Solyanik Reverted to the previous branch before System.Private.Windows.GdiPlus.dll was created and manually applied the code changes in AxHost.cs as recommended by Tanya. Built the branch and placed the generated DLLs in the .NET 10.0.100-alpha.1.24617.8 SDK. Verified the issue, and the parent control now correctly sends the WM_DESTROY message to the child controls during the disposal of ActiveX child controls.