When publishing AOT, C#/WinRT throws System.NotSupportedException: 'Cannot retrieve a helper type for generic public type 'Windows.Foundation.IAsyncOperation`1[System.Boolean]'.'

[smourier]

Description

I'm developing a WinUI3 application. When not publishing AOT, it works, but when adding <PublishAot>true</PublishAot>, it throws

System.NotSupportedException: 'Cannot retrieve a helper type for generic public type 'Windows.Foundation.IAsyncOperation`1[System.Boolean]'.'

Full stack trace:

[Exception] WinRT.Runtime.dll!WinRT.TypeExtensions.FindHelperType(System.Type type, bool throwIfNotAotSupported)	Unknown
[Exception] WinRT.Runtime.dll!WinRT.IWinRTObject.IsInterfaceImplementedFallback(System.RuntimeTypeHandle interfaceType, bool throwIfNotImplemented)	Unknown
[Exception] WinRT.Runtime.dll!WinRT.IWinRTObject.System.Runtime.InteropServices.IDynamicInterfaceCastable.IsInterfaceImplemented(System.RuntimeTypeHandle interfaceType, bool throwIfNotImplemented)	Unknown
Microsoft.Windows.SDK.NET.dll!Windows.Graphics.Printing.PrintManagerInterop.ShowPrintUIForWindowAsync(nint appWindow)	Unknown
WinUIApp.dll!WinUIApp.MainWindow.myButton_Click(object sender, Microsoft.UI.Xaml.RoutedEventArgs e) Line 19	C#
Microsoft.WinUI.dll!WinRT._EventSource_global__Microsoft_UI_Xaml_RoutedEventHandler.EventState.GetEventInvoke.AnonymousMethod__1_0(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)	Unknown
Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.RoutedEventHandler.Do_Abi_Invoke(nint thisPtr, nint sender, nint e)	Unknown
[Native to Managed Transition]	
[Managed to Native Transition]	
Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.IApplicationStaticsMethods.Start(WinRT.IObjectReference _obj, Microsoft.UI.Xaml.ApplicationInitializationCallback callback)	Unknown
Microsoft.WinUI.dll!Microsoft.UI.Xaml.Application.Start(Microsoft.UI.Xaml.ApplicationInitializationCallback callback)	Unknown
WinUIApp.dll!WinUIApp.Program.Main(string[] args) Line 26	C#

Steps To Reproduce

To reproduce just create a WinUI3 blank project with latest Visual Studio 17.12.0, and modify the MainWindow.xaml.cs like this:

using System;
using Microsoft.UI;
using Microsoft.UI.Xaml;
using Windows.Graphics.Printing;

namespace WinUIApp;

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private async void myButton_Click(object sender, RoutedEventArgs e)
    {
        var printMananager = PrintManagerInterop.GetForWindow(Win32Interop.GetWindowFromWindowId(AppWindow.Id));
        printMananager.PrintTaskRequested += (s, e) => { };
        await PrintManagerInterop.ShowPrintUIForWindowAsync(Win32Interop.GetWindowFromWindowId(AppWindow.Id));
    }
}

With standard settings, just run and it will fail on ShowPrintUIForWindowAsync with a COM exception but that's expected.

Now change the project settings to add PublishAot, and Rebuild (you must rebuild, a simple build is usually not enough here), here is mine:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net9.0-windows10.0.19041.0</TargetFramework>
    <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
    <RootNamespace>WinUIApp</RootNamespace>
    <ApplicationManifest>app.manifest</ApplicationManifest>
    <Platforms>x86;x64;ARM64</Platforms>
    <RuntimeIdentifiers>win-x86;win-x64;win-arm64</RuntimeIdentifiers>
    <PublishProfile>win-$(Platform).pubxml</PublishProfile>
    <UseWinUI>true</UseWinUI>
    <EnableMsixTooling>true</EnableMsixTooling>
    <Nullable>enable</Nullable>
    <PublishAot>true</PublishAot>
    <WindowsSdkPackageVersion>10.0.26100.57</WindowsSdkPackageVersion>
  </PropertyGroup>

  <ItemGroup>
    <Content Include="Assets\SplashScreen.scale-200.png" />
    <Content Include="Assets\LockScreenLogo.scale-200.png" />
    <Content Include="Assets\Square150x150Logo.scale-200.png" />
    <Content Include="Assets\Square44x44Logo.scale-200.png" />
    <Content Include="Assets\Square44x44Logo.targetsize-24_altform-unplated.png" />
    <Content Include="Assets\StoreLogo.png" />
    <Content Include="Assets\Wide310x150Logo.scale-200.png" />
  </ItemGroup>

  <ItemGroup>
    <Manifest Include="$(ApplicationManifest)" />
  </ItemGroup>

  <ItemGroup Condition="'$(DisableMsixProjectCapabilityAddedByProject)'!='true' and '$(EnableMsixTooling)'=='true'">
    <ProjectCapability Include="Msix" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.26100.1742" />
    <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.6.240923002" />
    <PackageReference Include="Microsoft.Windows.CsWinRT" Version="2.2.0" />
  </ItemGroup>

  <PropertyGroup Condition="'$(DisableHasPackageAndPublishMenuAddedByProject)'!='true' and '$(EnableMsixTooling)'=='true'">
    <HasPackageAndPublishMenu>true</HasPackageAndPublishMenu>
  </PropertyGroup>

  <!-- Publish Properties -->
  <PropertyGroup>
    <PublishReadyToRun Condition="'$(Configuration)' == 'Debug'">False</PublishReadyToRun>
    <PublishReadyToRun Condition="'$(Configuration)' != 'Debug'">True</PublishReadyToRun>
    <PublishTrimmed Condition="'$(Configuration)' == 'Debug'">False</PublishTrimmed>
    <PublishTrimmed Condition="'$(Configuration)' != 'Debug'">True</PublishTrimmed>
  </PropertyGroup>
</Project>

I've tried .NET 8 and 9, I've also tested with an explicit latest C#/WinRT and WindowsSdkPackageVersion references but it's the same.

Expected Behavior

It should not fail with a System.NotSupportedException.

Version Info

Visual Studio 17.12.0
C#/WinRT 2.2.0
.NET 9.0.0 or .NET 8.0.11

Additional Context

I don't know of any workaround, but it would be welcome.

[dongle-the-gadget]

In the meantime, the signature of this could be changed to return an IAsyncOperation<bool>, which should work with AOT mode:

CsWinRT/src/cswinrt/WinRT.Interop.idl

Line 82 in d6b7e97

Object ShowPrintUIForWindowAsync(

However, I don't think a more general solution to CsWinRT's existing usage pattern (casting from WinRT.IInspectable to a generic WinRT interface using IDynamicInterfaceCastable) would be possible without new projections).

[smourier]

Thanks,

Not sure if I'm supposed to do anything from here

[dongle-the-gadget]

Does MarshalInterface<IAsyncOperation<bool>>.FromAbi(MarshalInspectable<object>.FromManaged(printManager)); work?

[smourier]

Does MarshalInterface<IAsyncOperation<bool>>.FromAbi(MarshalInspectable<object>.FromManaged(printManager)); work?

but the problem is on PrintManagerInterop.ShowPrintUIForWindowAsync not on printManager?