Windows 10 IoT Core C++ Background Application referencing a C# Runtime Component

Question

I'm trying to use the Windows 10 IoT Core C++ Background Application (based on the MSFT IoT templates).

My scenario involves creating a native (C++) Background Application that leverages an existing managed (C#) Runtime Component. I can create such a solution in Visual Studio and it compiles and deploys to an IoT device just fine.

However, when I run the app, I see runtime exceptions like this anytime the managed component is used:

Exception thrown at 0x76C92052 in backgroundTaskHost.exe: Microsoft C++ 
exception: Platform::ClassNotRegisteredException ^ at memory location 
0x02B0F4A8. HRESULT:0x80040154 Class not registered

WinRT information: Class not registered

Stack trace:
[External Code]
backgroundapplicationcpp.dll!BackgroundApplicationCpp::StartupTask::
[Windows::ApplicationModel::Background::IBackgroundTask]::Run
(Windows::ApplicationModel::Background::IBackgroundTaskInstance ^ 
taskInstance) Line 13

Part of the promise of Windows Runtime is the interop of the languages (C++, C#, JS, VB) ... this scenario works just fine with a standard UWP app in place of an IoT Background Application.

How can this scenario work for Background Applications???

score 3 · Accepted Answer · edited Sep 03 '16 at 01:50

The part of the Visual Studio targets system that handles Background Applications is treating every library in the project as though it were the same language (C++) as the Background Application.

In this case, the managed Runtime Component is being treated like a C++ component. Because of this, the .NET libraries aren't being included in the deployment.

The next version of Visual Studio should contain a fix for this, but until then, I added this to my Background Application's vcxproj:

<!-- Workaround for bug in MSBuild regarding Native Background Applications referencing Managed Conponents -->
<PropertyGroup>
  <CopyNuGetImplementations>true</CopyNuGetImplementations>
  <NuGetRuntimeIdentifier>win10-$(PlatformTarget.ToLower())</NuGetRuntimeIdentifier>
</PropertyGroup>
<Target Name="_LocalResolvePrimaryProjectWinmdFiles" BeforeTargets="BeforeGenerateAppxManifest" AfterTargets="_ResolvePrimaryProjectWinmdFiles" Condition="'$(OutputType)' != 'exe' and '$(AppxPackage)' == 'true' AND '$(ContainsStartupTask)' == 'true'">
  <ItemGroup>
    <_AppxWinmdFilesToHarvest Remove="@(_AppxWinmdFilesToHarvest)" />
    <_AppxWinmdFilesToHarvest Include="@(PackagingOutputs)" Condition="'%(PackagingOutputs.Extension)' == '.winmd' and '%(PackagingOutputs.ProjectName)' == '$(ProjectName)' and '%(PackagingOutputs.ResolvedFrom)' != 'GetSDKReferenceFiles'">
      <!-- This covers the Managed Background Application winmd which does NOT have a WinMDFileType value set -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' == ''">WindowsRuntime 1.4;CLR v4.0.30319</ImageRuntime>
      <!-- This covers the C++ Background Application winmd which does NOT have a WinMDFileType value set -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' == '' and '@(Language)' == 'C++'">WindowsRuntime 1.4</ImageRuntime>
      <!-- This covers Managed Windows Runtime Component winmds -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' == '' and '%(PackagingOutputs.WinMDFileType)' == 'Managed'">WindowsRuntime 1.4;CLR v4.0.30319</ImageRuntime>
      <!-- This covers Native Windows Runtime Component winmds -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' == '' and '%(PackagingOutputs.WinMDFileType)' == 'Native'">WindowsRuntime 1.4</ImageRuntime>
      <!-- This covers Native Windows Runtime Component winmds for DynamicLibrary projects -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' == '' and '%(PackagingOutputs.ProjectType)' == 'DynamicLibrary'">WindowsRuntime 1.4</ImageRuntime>
      <!-- This provides an override -->
      <ImageRuntime Condition="'$(PrimaryProjectWinmdImageRuntimeOverride)' != ''">$(PrimaryProjectWinmdImageRuntimeOverride)</ImageRuntime>
    </_AppxWinmdFilesToHarvest>
  </ItemGroup>
</Target>

With that block of code, the .NET libraries are deployed with the Background Application and the native code can successfully access the managed component.

Windows 10 IoT Core C++ Background Application referencing a C# Runtime Component

1 Answers1