“COMException” when reunion app launched without deployment

[eugene-lerner]

I created a new app using “Blank App, Packaged (WinUI in Desktop)” template; it contains a single button prompting to click it.

The solution, generated by Visual Studio 2019 Enterprise, contains two projects – Windows Application and Package. When the Package project is set as “Startup” the app gets deployed and runs OK. Problem arises when Windows Application project is set as “Startup”:

COMException: Class not registered (0x80040154 (REGDB_E_CLASSNOTREG))

I’m also getting the following exception when double-click compiled executable in Windows Explorer (from Windows Event Viewer):

Application: MSSample2.exe
CoreCLR Version: 5.0.421.11614
.NET Version: 5.0.4
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.Runtime.InteropServices.COMException (0x80040154): Class not registered (0x80040154 (REGDB_E_CLASSNOTREG))
   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode)
   at WinRT.BaseActivationFactory..ctor(String typeNamespace, String typeFullName)
   at Microsoft.UI.Xaml.Application._IApplicationStatics..ctor()
   --- End of inner exception stack trace ---
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean wrapExceptions, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& hasNoDefaultCtor)
   at System.RuntimeType.CreateInstanceDefaultCtorSlow(Boolean publicOnly, Boolean wrapExceptions, Boolean fillCache)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, Boolean wrapExceptions)
   at System.Activator.CreateInstance[T]()
   at WinRT.WeakLazy`1.get_Value()
   at Microsoft.UI.Xaml.Application._IApplicationStatics.get_Instance()
   at Microsoft.UI.Xaml.Application.Start(ApplicationInitializationCallback callback)
   at MSSample2.Program.Main(String[] args) in <path>\obj\x86\Debug\net5.0-windows10.0.19041.0\App.g.i.cs:line 26

What is the cause for “COMException”?
How to launch WinUI as a desktop application without deploying it first?

Thank you,

Eugene

[mrlacey]

This isn't yet a supported scenario.
You have to use the packaged app. For now...

[andrewleader]

Thanks Matt for answering! To add on, 0.8 will add preview support for unpackaged apps, you can see our roadmap here: https://github.com/microsoft/ProjectReunion/blob/main/docs/roadmap.md

In the meantime, you must use the packaging project as your startup project and deploy via MSIX.