Specified cast is not valid while using as WinRT server on net8.0

[hez2010]

Hello, thanks for the project.

I'm trying to use it to create a WinRT server with CsWinRT to run on net8.0, and here is the project I'm using for testing: https://github.com/hez2010/WinRTServerTest

I copy-pasted your library code because in net8.0 the IActivationFactory interface type will fail to load, so I removed the : IActivationFactory from BaseActivationFactory.

The ActivationFactory can be created successfully, but when activating the class TestClass, it failed to cast the managed object (an instance of TestClass) to IInspectable at unkwnPtr.CopyTo(instance) in BaseActivationFactoryProxy.ActivateInstance with Specified cast is not valid..

Shmuelie.WinRTServer/src/Shmuelie.WinRTServer/Internal/BaseActivationFactoryProxy.cs

Line 233 in 8bfa82e

int result = unkwnPtr.CopyTo(instance);

[shmuelie]

Yeah, the server components highly rely on the built in COM/WinRT marshaling. I've started working on support for "modern" .NET code but it's not working yet.

[shmuelie]

I got the COM Server working on modern .NET. Working on WinRT server now

[shmuelie]

Ok, @hez2010 try using https://github.com/shmuelie/Shmuelie.WinRTServer/pkgs/nuget/Shmuelie.WinRTServer/158852442 and if that works, I'll prepare a full release for nuget.org

[hez2010]

Hello, thanks for the investment into modern .net support for WinRT.

I tested it with a simple test project https://github.com/hez2010/WinRTServerTest but unfortunately it still failed with Interface was not supported.
However, this time the instance on the server (WinRTServer) can be activated successfully, but soon it failed at VftblIUnknown.QueryInterface(ThisPtr, &iid, &thisPtr); in WinRT.IObjectReference.TryAs on the client side (WinRTServerTest) with HRESULT 0x80004002.

Is there anything I'm missing in the test project?

[hez2010]

I suspect this is an issue from CsWinRT as I hit the same exception while using RoRegisterActivationFactories manually.
Opened an issue there: microsoft/CsWinRT#1419

[shmuelie]

Ok, I looked at your test project and you're missing the Metadata and interface projects that my sample shows. I admit having them is a pain but I haven't been able to get away from them yet

[hez2010]

I see. I just added the interface and metadata projects but still with no luck.
You may see the simple test project here: https://github.com/hez2010/WinRTServerTest/tree/metadata

[shmuelie]

The TestClass type needs to have a GuidAttribute like https://github.com/shmuelie/Shmuelie.WinRTServer/blob/main/tests/Shmuelie.WinRTServer.Sample.Server/RemoteThing.cs does

[hez2010]

Still no luck even if with a GuidAttribute added to the TestClass.
And note that if I downgrade the server project to net7.0-windows10.0.22621.0, it will fail at Specified cast is not valid at unkwnPtr.CopyTo(instance) again as the top-most post of this issue.

[shmuelie]

The ITestCase needs to use the Windows.Foundation.Metadata.GuidAttribute attribute, not the System.Runtime.InteropServices.GuidAttribute attribute.

[hez2010]

Still not working even with Windows.Foundation.Metadata.GuidAttribute. I'm going to create a new project and see if it works.

[shmuelie]

@hez2010 if that doesn't work, could you see if the test projects in the modern-net branch work for you?

[hez2010]

I changed my client from net8.0 to net481 while kept the server project net8.0 and this time it works as expected.
Seems that it's definitely a CsWinRT issue.

[shmuelie]

That is very weird as Shmuelie.WinRTServer.Sample.WpfNet6Client worked for me with the WinRT Activation of a .NET 8 server.

[hez2010]

Yeah, it's very weird as your sample also works for me...

Here is the repro: https://github.com/hez2010/WinRTServerRepro
It will only work if you change the TFM of WinRTServer.Client/WinRTServer.Client.csproj from net8.0-windows10.0.22621.0 to net481.

[hez2010]

It turns out to be my fault that I didn't copy the winmd files next to the client exe.
Now it works as expected.

Anyway, a big thanks for your work, and feel free to close this issue and release the new package :)

[shmuelie]

Nice. I'll try to make some improvements to the documentation first but awesome!

[shmuelie]

@hez2010 version 1.2.0 published to nuget!