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Hi HN, I'm Giovanni, founder of Userware. We built XAML.io, a free browser-based IDE for C# and XAML that compiles and runs .NET projects entirely client-side via WebAssembly. No server-side build step.

The link above opens a sample project using Newtonsoft.Json. Click Run to compile and execute it in your browser. You can edit the code, add NuGet packages, and share your project via a URL.

What's new in v0.6:

- NuGet package support (any library compatible with Blazor WebAssembly) - Code sharing via URL with GitHub-like forking and attribution - XAML autocompletion, AI error fixing, split editor views

The visual designer is the differentiator: 100+ drag-and-drop controls for building UIs. But the NuGet and sharing features work even if you ignore the designer entirely and just write C# code.

XAML.io is currently in tech preview. It's built on OpenSilver (https://opensilver.net), a from-scratch reimplementation of the WPF API (subset) using modern .NET, WebAssembly, and the browser DOM. It's open-source and has been in development for over 12 years (started as CSHTML5 in 2013, rebranded to OpenSilver in 2020).

Limitations: one project per solution, no C# IntelliSense yet (coming soon), no debugger yet, WPF compatibility improvements underway, desktop browsers recommended.

Full details and screenshots: https://blog.xaml.io/post/xaml-io-v0-6

Happy to answer questions about the architecture, WebAssembly compilation pipeline, or anything else.