Microsoft Releases Experimental C# WinUI Framework
The framework enables code-first interface design to streamline native Windows 11 development.
Updated on Oct. 22, 2026 in Software
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Microsoft has released Microsoft.UI.Reactor, an experimental C# framework designed to allow developers to build native WinUI applications entirely in code. This research-stage framework integrates over 60 automated code checks to identify performance and accessibility issues during development.
Why it matters
Microsoft aims to lower the barrier for developers building native Windows 11 applications by offering a code-first alternative to XAML. The initiative seeks to improve app quality and minimize the reliance on web-based wrappers on the Windows platform.
Microsoft.UI.Reactor enables developers to describe user interfaces directly in C# rather than using XAML, maintaining application state across code edits. The framework includes over 60 built-in diagnostic checks to monitor dark mode, accessibility, and performance metrics.
The players
Microsoft
A global technology leader maintaining the Windows operating system, the .NET development ecosystem, and the WinUI framework.
The details
The framework operates by using C# to render WinUI controls and primitives, bypassing the need for declarative XAML files. It incorporates automated validation tools that scan code for performance bottlenecks or accessibility flaws during the build process, providing immediate feedback. While Reactor introduces a code-first paradigm, XAML remains a supported and actively invested format for WinUI development.
Timeline
October 2026: Microsoft released documentation for the Microsoft.UI.Reactor framework.
May 2026: Microsoft committed to continued development of the WinUI ecosystem.
The Tech Race
The introduction of Reactor signals an effort to modernize the WinUI development experience to compete with cross-platform frameworks. It builds upon the existing WinUI ecosystem while offering a departure from traditional XAML workflows.
Developers building for Windows 11 can now access this experimental framework to streamline interface construction using C#. The tool remains in the research stage, meaning it is not yet intended for production-grade, commercial application deployment.
The takeaway
Microsoft is testing whether a code-centric interface design can simplify native Windows app development. Developers should monitor the project's documentation to see if it receives a transition to a stable production release in future updates.
Further reading
Learn more about the latest developments in the Software ecosystem.
Source note: This article includes information reported by Windows Latest.
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