C++/WinRT Plus

C++/WinRT Plus is a community-driven evolution of the original C++/WinRT project. This independent initiative is neither affiliated with nor sponsored by Microsoft. Our mission is to address long-standing issues in C++/WinRT and deliver meaningful improvements to the developer experience. While the project introduces some breaking changes, we provide a simple and smooth migration path. You can continue using it just as you would with C++/WinRT.

We're deeply grateful to the original authors of C++/WinRT for their groundbreaking work, which gave the C++ community first-class access to the Windows Runtime.

With development on the original project slowing, we believe it's time for the community to take the lead. C++/WinRT Plus builds on that strong foundation—preserving what works while addressing the issues that matter most to daily users. Join us in shaping the future of Windows Runtime development in C++.

How to use

You can install the package directly via NuGet with the ID YexuanXiao.CppWinRTPlus.

Roadmap

The current plans for C++/WinRT Plus can be viewed in the issue list. C++/WinRT Plus currently has many ambitious improvements, so your help is greatly needed!

Changelog

Since the C++/WinRT mainline has accepted our module implementation, C++/WinRT Plus is now rebased onto the C++/WinRT 3.0 mainline to maintain compatibility.

All the changes listed here only show the differences from the C++/WinRT mainline, and once the C++/WinRT Plus commits are merged upstream, they will be removed.

2026/09/17:

1. C++/WinRT Plus can now work with our VSIX extension to provide visualization for WinRT types in third-party NuGet packages (such as WindowsAppSDK).
2. Fixed the issue where XamlMetadataProvider.cpp still requires the pch.h even when it is disabled.
3. Optimized the performance of winrt::to_string using C++23's new resize_and_overwrite function.

2026/03/24: Support using lambdas with explicit object parameter as delegates to resolve the issue where the captured lifetime may be shorter than the lifetime of the coroutine frame.

The C++/WinRT language projection

C++/WinRT is an entirely standard C++ language projection for Windows Runtime (WinRT) APIs, implemented as a header-file-based library, and designed to provide you with first-class access to the modern Windows API. With C++/WinRT, you can author and consume Windows Runtime APIs using any standards-compliant C++17 compiler.

• Documentation: https://aka.ms/cppwinrt
• NuGet package: http://aka.ms/cppwinrt/nuget
• Visual Studio extension: http://aka.ms/cppwinrt/vsix
• Wikipedia: https://en.wikipedia.org/wiki/C++/WinRT

Building C++/WinRT

Don't build C++/WinRT yourself - just download the latest version here: https://aka.ms/cppwinrt/nuget

Working on the compiler

If you really want to build it yourself, the simplest way to do so is to run the build_test_all.cmd script in the root directory. Developers needing to work on the C++/WinRT compiler itself should go through the following steps to arrive at an efficient inner loop:

• Open a dev command prompt pointing at the root of the repo.
• Open the cppwinrt.sln solution.
• Choose a configuration (x64, x86, Release, Debug) and build projects as needed.

If you are working on an ARM64 specific issue from an x64 or x86 host, you will need to instead:

• Open the cppwinrt.sln solution
• Build the x86 version of the "cppwinrt" project first
• Switch to your preferred configuration and build the test binaries and run them in your test environment

Comparing Outputs

Comparing the output of the prior release and your current changes will help show the impact of any updates. Starting from a dev command prompt at the root of the repo after following the above build instructions:

• Run build_projection.cmd in the dev command prompt
• Run build_prior_projection.cmd in the dev command prompt as well
• Run prepare_versionless_diffs.cmd which removes version stamps on both current and prior projection
• Use a directory-level differencing tool to compare _build\$(arch)\$(flavor)\winrt and _reference\$(arch)\$(flavor)\winrt

Testing

This repository uses the Catch2 testing framework.

• From a Visual Studio command line, you should run build_tests_all.cmd to build and run the tests. To Debug the tests, you can debug the associated _build\$(arch)\$(flavor)\<test>.exe under the debugger of your choice.
• Optionally, you can install the Catch2Adapter to run the tests from Visual Studio.