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Jan Jones @janjones.me · 28/02/2026

Bound trees (internal Roslyn representation of executable code) can now be displayed on .NET Lab. This includes ref safety escape scopes. Makes investigation of compiler bugs easier. #dotnet #csharp #roslyn #dotnetlab

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Jan Jones @janjones.me · 23/12/2025

Yes, that should be possible with the desktop framework I'm currently using (Photino). Good to know there is demand for that, thanks, I will try looking into that soon.

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Jan Jones @janjones.me · 23/12/2025

Proper links can't be created in the official bluesky app afaik (but it can render them 🤷‍♂️), so I'm using @deck.blue for that.

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Jan Jones @janjones.me · 22/12/2025

.NET Lab can now display disassembled machine code. It's taken directly from JIT, hence only supported on desktop for now. #dotnet #csharp #roslyn #asm #dotnetlab

Screenshot of .NET Lab with disassembled machine code

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Jan Jones @janjones.me · 17/12/2025

Tired of waiting for the WebAssembly version of .NET Lab to load? There is now .NET Lab Desktop for Windows which is much faster thanks to running on full .NET: apps.microsoft.com/detail/9PCPM... ⚡

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Jan Jones @janjones.me · 16/12/2025

Yes, pinning an exact version is what I meant. Although that wouldn't affect design time (IntelliSense), only builds.

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Jan Jones @janjones.me · 16/12/2025

You can leave it unset (or set to empty). That makes it automatically determined from the TargetFramework. If you set it to latest/preview (recommended eg if you multitarget), you should also pin the SDK version in global.json to ensure consistent value regardless of the actual SDK used to build.

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Reposted by Jan Jones

nohwnd @jakubjares.com · 08/12/2025

Getting ready for our last .NET meetup Prague of the year. This time with a holiday vibe! #dotnet aka.ms/DotnetMeetup...

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Jan Jones @janjones.me · 14/11/2025

Great feature I've got a chance to work on in .NET 10

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Jan Jones @janjones.me · 13/11/2025

I believe debugging picks up arguments that you specify in launchSettings.json (or *.run.json - github.com/dotnet/sdk/i...)

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Jan Jones @janjones.me · 05/10/2025

Yes, it should work. .NET 10 rc1 is even the version of compilers included by default. I just tried what you described but it works fine for me. Can you try in a fresh private window, perhaps there are some old files interfering?

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Jan Jones @janjones.me · 05/10/2025

Fully revamped the tree view 🌳 in .NET Lab. Now with cursor syncing. Can display syntax, IOperation, and symbol info. #dotnet #csharp #roslyn #dotnetlab

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Reposted by Jan Jones

Damian Edwards @damianedwards.com · 11/09/2025

Big improvements to the performance of developing C# file-based incoming. Subsequent builds/runs will cache MSBuild outputs & directly invoke the C# compiler if inputs don't change. This in addition to the work in rc.1 to avoid MSBuild completely for simple file-based apps github.com/dotnet/sdk/p...

github.com

Reuse CSC arguments in file-based app runs by jjonescz · Pull Request #50635 · dotnet/sdk

Part of #48011. This optimization saves CSC arguments when MSBuild runs and then reuses them in subsequent runs so dotnet run file.cs can skip MSBuild and invoke only the compiler. In my simple exp...

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Jan Jones @janjones.me · 06/09/2025

Added a small but useful feature to copy the current URL in .NET Lab (lab.razor.fyi). It has a keyboard shortcut too: Ctrl+; 📋 #dotnet #csharp #roslyn #dotnetlab

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Jan Jones @janjones.me · 26/07/2025

.NET Lab (lab.razor.fyi) just gained new configuration options inspired by `dotnet run app.cs`. Reference any NuGet packages via `#:package` or quickly change config via `#:property` (with editor suggestions to guide you). 🚀⚙️

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Reposted by Jan Jones

Damian Edwards @damianedwards.com · 15/07/2025

Check out all the improvements to file-based apps (dotnet run app.cs) in preview.6 that went out today! github.com/dotnet/core/...

github.com

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Reposted by Jan Jones

Andrew Lock "Sock" @andrewlock.bsky.social · 08/07/2025

Blogged: Behind the scenes of dotnet run app.cs - Exploring the .NET 10 preview - Part 2 andrewlock.net/exploring-do... In this post I looks at how the new single-file .NET run experience is implemented inside the .NET SDK, focusing on how the virtual-project file is built. #dotnet #csharp

andrewlock.net

Behind the scenes of dotnet run app.cs: Exploring the .NET 10 preview - Part 2

In this post I looks at how the new single-file .NET run experience is implemented inside the .NET SDK, focusing on how the virtual-project file is built

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Jan Jones @janjones.me · 28/06/2025

.NET Lab (lab.razor.fyi) now has Code Actions 🚀 Very useful when you paste some code snippet and want to add missing usings. But it can do much more - all Roslyn code fixes are included.

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Jan Jones @janjones.me · 22/06/2025

Added semantic highlighting to .NET Lab (lab.razor.fyi)

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Jan Jones @janjones.me · 15/06/2025

Yes, should be in .NET 10 Preview 6

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Jan Jones @janjones.me · 16/05/2025

Completions and live diagnostics are now much improved and enabled by default in .NET Lab (lab.razor.fyi). Stay tuned for more enhancements to the editing experience coming soon.

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Jan Jones @janjones.me · 02/03/2025

Shared lab.razor.fyi snippets are now cached, so you can see the output even before the compiler is initialized. (Nevertheless, more optimizations of loading times are coming.) Example: lab.razor.fyi#47Lm4gooyk8v...

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Jan Jones @janjones.me · 21/02/2025

Added this cool loading animation to lab.razor.fyi. Suddenly the loading feels faster ⚡

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Jan Jones @janjones.me · 20/12/2024

Old version using Bootstrap

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Jan Jones @janjones.me · 20/12/2024

Updated lab.razor.fyi to use Microsoft Fluent UI. Quite happy with the result. Also got dark mode for free.

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