Union types are coming to C#. That alone made Build 2026 worth watching. But also: dotnetup (SDK installs per-project), on-device AI with MAUI, agentic web apps with ASP.NET Core. Full session guide in the reply.

New blog: Migrating from ArcGIS Online: Watch Out for GeoJSON Winding Order bertt.wordpress.com/2026/06/…

Start of week serious energy: Fully responsive Enterprise CRM app. Works across Web, Mobile & Desktop. Integrations with LiveCharts & MapsUI. github.com/samidip/UnoCRMDas… Cross-platform by nature with @UnoPlatform. Built with GitHub Copilot & Sonnet.

oh boy! 🙀5.1.0 was released. Look at those release notes: github.com/Mapsui/Mapsui/rel…

We're on fire 🔥 Released v5.1 beta.8 Monday and beta.9 Tuesday. Updated SkiaSharp to 3.119.2 and bunch of fixes #dotnet #mapsui Release notes: github.com/Mapsui/Mapsui/rel… github.com/Mapsui/Mapsui/rel…

Anders Hejlsberg (@ahejlsberg) is a living legend: he created Turbo Pascal, Delphi, C# and TypeScript (and today TypeScript is the most-used programming language, globally, as per GitHub.) Timestamps: 00:00 Intro 02:48 How Anders got into programming 05:40 Building his first compiler 07:44 Turbo Pascal 12:25 Delphi 14:53 Joining Microsoft 19:41 Building C# 29:11 Async/await 34:01 The rise of JavaScript 37:52 Building TypeScript 42:58 How the TypeScript compiler works 48:30 JavaScript’s strengths and weaknesses 52:18 How Anders uses AI 56:03 What language features work well with AI 1:02:49 How software craftsmanship is changing 1:07:49 Performance and efficiency 1:09:29 Anders’ tool stack 1:11:30 A 30-year career at Microsoft 1:13:40 Book recommendation Brought to you by: @AntithesisHQ – verify your system’s correctness without human review or traditional integration tests – and avoid bugs or outages. antithesis.com/pragmatic @WorkOS – Everything you need to make your app enterprise ready. WorkOS.com @turbopuffer – a vector and full-text search engine built on object storage. It’s fast, cheap, and extremely scalable. turbopuffer.com/pragmatic Four things that stood out to me: 1. “10x better for 1/10th of the price” is a proven winner. This is what Turbo Pascal did: it sold for $49.95 when competing compilers cost $500, and it was faster and more interactive than competitors’ products. Conveniently, the low price tag also killed off piracy 2. C# might have not existed without a famous court case. Microsoft originally hired Anders to architect its Java tools (Visual J ), but the Sun versus Microsoft lawsuit (1997-2001) meant Microsoft could not build on top of Java, as the company that owned Java’s IP (Sun) sued MS for alleged unauthorized changes to the Java language. Microsoft realized it had to build a new language that combined VB’s productivity with C ’s power. This led to C# and .NET. 3. TypeScript exists because Anders refused to build Script# for the Outlook .com team. Microsoft’s Outlook .com team asked Anders’ C# team to productize “ScriptSharp,” a language to cross-compile C# to JavaScript. Anders and the C# team pushed back, suggesting that a better approach was to fix JavaScript. Anders felt strongly that to be attractive to the best-of-breed developers in the JavaScript ecosystem, you want people to write JavaScript, and not another language like C#. 4. Designing a programming language is a 10-year play. As Anders puts it: “Version one is great, but has all sorts of issues. You’ve got to do version two, but it’s not until version three that it really starts to be great. Then you’ve got to convince people to adopt it.”

Avalonia 12 support was added to Mapsui 5.1.0-beta.7 🎉We had quite some requests for this. Can I have some cheers from the Avalonia community? Release notes: github.com/Mapsui/Mapsui/rel… @AvaloniaUI @MikeCodesDotNET

Updated to the latest Uno 5 SDK 🎉 Sorry for the delay. Can I get some cheers from the Uno side? Release notes: github.com/Mapsui/Mapsui/rel… @UnoPlatform @wieslawsoltes @mzikmunddev @matteiomattei @BiloganSteve

Fix: Font.FontSource - point it at a font file that covers your script. FontSource = "file:///fonts/NotoSansSC.ttf" Works for LabelStyle, CalloutStyle, and now Widgets too. Tip: Google's Noto fonts cover virtually every script. fonts.google.com/noto Requires experimental mode.

Making TextBlock measure 333x times faster (yes its 33x times faster) in Avalonia thanks to PretextSharp

Built a static transit app for the Netherlands — 52,000 stops, all operators, no backend. Because all other planners are pure shit 💩 🔗 bertt.github.io/OVNu/ (bertt.github.io/OVNu/) #GTFS #OpenData #PublicTransit

🚀 Mapsui 5.1.0-beta.6 is out! It fixes a memory leak in MAUI Release notes: github.com/Mapsui/Mapsui/rel… #dotnetMAUI #mapsui #dotnet

So you want to write games with .NET, now you can powered by @SkiaSharp new mesh api and shaders paired with @UnoPlatform here is just example what can be done.

I love how "being written in rust" is now part of the selling point of many dev tools... 🙃🙃🙃

Me: Do this thing AI: This is a massive task Me: Yeah, do it AI: It’s truly massive and requires editing 205 files Me: Yeah, Microsoft is 10x’ing their price. Now get to work! AI: …

🗺️ New in the latest beta: GridLayer! Overlay a coordinate grid on your Mapsui map with just one line of code: map.Layers.Add(new GridLayer { ShowCoordinateLabels = true }); Try the live sample 👇 mapsui.com/v5/samples/#/Spec… #dotnet #csharp #mapping #opensource

Did you know Mapsui supports TEN different .NET UI frameworks? 🤯 Whether you build with MAUI, Avalonia, Uno Platform, Blazor, WPF, or WinUI, we've got your mapping needs covered with a single shared codebase. 🌍💻 mapsui.com/v5/ #dotnet #avaloniaui #blazor