Niels Swimburger.NET 🍔

How we enforce web API standards and guidelines at Workleap We automate API specs as first class citizens, keeping them versioned, validated, and checked for breaking changes in ASP.NET Core projects.

Extract OpenAPI specs from #dotnet web apps automatically. Fail CI checks if the spec isn't synced with #csharp code, validate it against Spectral rules, and catch breaking changes. All handled at build time by a single NuGet package made at Workleap.

medium.com/p/8a535d813244

How to generate a TypeScript SDK for your API spec | Fern Learn how to deliver a TypeScript SDK that’s lightweight, fully type-safe, and works across all JavaScript runtimes with Fern.

Having experienced these challenges firsthand at AssemblyAI, I'm now working full-time on a TypeScript generator at Fern. I've written about today's development challenges and what it takes to deliver exceptional TypeScript SDKs in 2025.

buildwithfern.com/post/generat...

Now I'm building libraries that need to work seamlessly across browsers, multiple Node.js versions, Bun, Deno, edge runtimes like Cloudflare Workers and Vercel Edge Runtime, and yes, React Native too. The complexity has exploded, but our tooling hasn't kept pace.

I've been working with JavaScript since the days when browser compatibility was our biggest headache. Supporting IE6 and the original Edge alongside Chrome and Firefox felt challenging at the time. But that was nothing compared to today's reality.

Watch @damianedwards.com blow your mind with the demo!

youtu.be/98MizuB7i-w

#dotnet #csharp

Announcing TypeScript Native Previews - TypeScript Previews of the native TypeScript port are now available on npm and for VS Code through the Visual Studio Marketplace!

devblogs.microsoft.com/typescript/a...

Beautiful

YouTube video by Veritasium How One Company Secretly Poisoned The Planet

youtu.be/SC2eSujzrUY?...

I went on holiday for two weeks and I feel like VSCode + Copilot improved a lot in just that little time.
It feels a lot smoother and better predictions.

New async Zip APIs in .NET 10 preview 4! Fantastic that this gap is bridged :)
github.com/dotnet/core/...

Proxyman · Debug, intercept & mock HTTP with Proxyman Proxyman is a native, high-performance macOS app, which enables developers to capture, inspect, and manipulate HTTP/HTTPS requests/responses with ease. Support iOS and Android Simulator and Physical D...

My favorite dev tool this year has been Proxyman. It's a well crafted super useful tool for anyone working with HTTP APIs.
Money very well spent!

proxyman.com

I was able to achieve a pretty good UX cobbling together some System.Text.Json extensibility points. Feedback appreciated!

Join the Fern team We are a small, tight-knit team building dev tools for the largest API-first companies in the world. We’re also musicians, DJs, photographers, wine enthusiasts, runners, and more.

Check out our roles: buildwithfern.com/careers

Jack (labradoodle) with role Barkitect

Want to work on really cool developer facing products?
We have a couple of open roles in Brooklyn and you get a proximity bonus for living nearby!

The best perk is the support from Chief Barkitect Jack.

BRING BACK DYNAMIC

How to create a symmetrical JSON class for reading and writing that is intuitive with [JsonExtensionData]? · Issue #114106 · dotnet/runtime We're experimenting with how we can provide the most intuitive, developer friendly experience for reading and writing additional properties for OpenAPI and are struggling to use [JsonExtensionData]...

Anyone using [JsonExtensionData] in .NET that has suggestions here?
github.com/dotnet/runti...

We’re excited to launch Square's .NET SDK today, git.new/1WyYbPA! We sweat over the details so Square doesn't have to — here’s what makes this release stand out: (1/3)

GitHub - square/square-dotnet-sdk: .NET client library for the Square API .NET client library for the Square API. Contribute to square/square-dotnet-sdk development by creating an account on GitHub.

Check it out: github.com/square/square-dotnet-sdk

⚡ P.S. Also optimized webhook signature verification with Span<char> & Span<byte> to reduce allocations.

GitHub - square/square-dotnet-sdk: .NET client library for the Square API .NET client library for the Square API. Contribute to square/square-dotnet-sdk development by creating an account on GitHub.

Just shipped Square's .NET SDK:
🔄 Modern C# & .NET with .NET Framework 4.6.2 compatibility
📦 System.Text.Json (no Json.NET) with minimal dependencies
✨ IAsyncEnumerable pagination, discriminated unions & forward-compatible enums
🧪 300+ tests including 88 migrated integration tests

feat: Optimize request validator + make thread safe (backwards compatible) by Swimburger · Pull Request #660 · twilio/twilio-csharp All third-party contributors acknowledge that any contributions they provide will be made under the same open-source license that the open-source project is provided under. ASP.NET Core is pushing ...

You get the brightest people in the .NET community to review your PR, but clearly Twilio doesn't care about C# or .NET.
github.com/twilio/twili...

I'm done with Twilio 🤡

.NET 9 Networking Improvements - .NET Blog Introducing new networking features in .NET 9 including HTTP space, HttpClientFactory, security and more!

devblogs.microsoft.com/dotnet/dotne...

Jobs at Fern | Y Combinator Jobs at Fern

We're looking for a front-end, back-end, AI, and a deployed engineer at Fern, come work for with an awesome team in Brooklyn NY
www.ycombinator.com/companies/fe...

YouTube video by keshi - Topic 2 soon

music.youtube.com/watch?v=LKZy...

Yup

Exactly

The deployment is pushing to NuGet, so not really anything to install there. Just installing the runtime on the GHA machine itself before running tests.

yes, but you can't run them, for the test project I need the runtime to be present.

Global.json wouldn't work well here because I'm using .NET 9, but the test project may and in many cases is a different version.

I'm using the .NET 9 SDK because it has new package vulnerability reporting and other improvements, but it could be any future version SDK. The GH actions is not for one repo but for many repos and the .NET version of the test project isn't under my full control.