I have created a File Explorer context menu extension that uses the IExplorerCommand interface to add menu commands to the Windows 11 context menu.
This has been working fine, but after the last Windows update, it no longer works properly.
Although the menu commands still appear, nothing happens when I click on any of them. I've added logging and I can see that IExplorerCommand::Invoke() is no longer being called.
Strangely, if I select the "Show more options" menu to get the legacy Windows 10 context menu, the commands work fine from that menu, it is only in the new Windows 11 context menu that they don't work.
I have tried running File Explorer in a debugger while selecting my menu commands, and I get lines like this in the output window when I click on the command:
onecore\com\combase\dcomrem\stdid.cxx(726)\combase.dll!00007FF9EB9947F5: (caller: 00007FF9C22E1E38) ReturnHr(2627) tid(67bc) 8001010E The application called an interface that was marshalled for a different thread.
I'm guessing this is the reason why my commands are not being called. Does anyone have any suggestions for what is causing this? Could it be a bug in File Explorer?
I've tried both STA and MTA threading models, and changing this made no difference.
Well, after wasting hours on this I finally have a solution!
My code was based on the PhotoStoreContextMenu sample code here: https://github.com/microsoft/AppModelSamples/tree/master/Samples/SparsePackages/PhotoStoreContextMenu
This uses the Windows Runtime C++ Template Library (WRL), and defines the base classes used by the class like this:
class TestExplorerCommandBase : public RuntimeClass<RuntimeClassFlags<ClassicCom>, IExplorerCommand, IObjectWithSite>
The change that fixed it for my code was to use WinRtClassicComMix instead of ClassicCom, i.e.
class TestExplorerCommandBase : public RuntimeClass<RuntimeClassFlags<WinRtClassicComMix>, IExplorerCommand, IObjectWithSite>
I'm pretty sure this problem started when I installed KB5019509, which is the Windows update that changes File Explorer so that it now has tabs.
Note: this problem only happens for IExplorerCommands created in the plug-in for submenus, the top level commands that are defined in the APPX file work fine.
Also note that although this change does fix the problem with Invoke() not being called, it does introduce a new problem which is that IOleWindow::GetWindow() no longer works so it is not possible to get the parent HWND. (See Calling IOleWindow::GetWindow() from IExplorerCommand::Invoke() is giving error 8001010d (RPC_E_CANTCALLOUT_ININPUTSYNCCALL)).