Modernizing UWP to .NET 9 on HoloLens 2

This sample demonstrates how to modernize a UWP app for HoloLens 2 using .NET 9. It shows how to reference native WinRT components, such as HoloLens2ResearchMode, and integrate the Microsoft.MixedReality.QR NuGet package in a .NET 9 C# project.

Features

• Targets .NET 9.0 with net9.0-windows10.0.22621.0
• Uses CsWinRT to interop with native WinRT components
• Supports direct referencing of C++/WinRT .vcxproj projects
• Demonstrates HoloLens 2 sensor access and QR code tracking
• Enables access to Research Mode sensors (depth, IR, etc.)

Referencing WinRT Components

To consume WinRT components like HoloLens2ResearchMode, add the following to your .csproj:

<PropertyGroup>
  <CsWinRTIncludes>HoloLens2ResearchMode</CsWinRTIncludes>
  <CsWinRTGeneratedFilesDir>$(OutDir)</CsWinRTGeneratedFilesDir>
</PropertyGroup>

• CsWinRTIncludes: Specifies the WinRT namespace to include.
• CsWinRTGeneratedFilesDir: Points to the output directory containing generated interop files.

With this setup, the C# project can directly use types from the native component.

Using Microsoft.MixedReality.QR

The Microsoft.MixedReality.QR NuGet package may include an incorrect native DLL when used in a .NET 9 UWP app, causing a runtime exception where StereoKit fails to load.

To ensure proper interop, manually include the .winmd file for CsWinRT projection and the correct native arm64 DLL:

<ItemGroup>
    <CsWinRTInputs Include="../Microsoft.MixedReality.QR/0.5.3037/lib/uap10.0.18362/Microsoft.MixedReality.QR.winmd" />
    <Content Include="../Microsoft.MixedReality.QR/0.5.3037/runtimes/win10-arm64/native/Microsoft.MixedReality.QR.dll"
             CopyToOutputDirectory="PreserveNewest"
             Visible="false" />
</ItemGroup>

This setup ensures CsWinRT generates the correct C# projection and that the appropriate native DLL is included.