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?

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

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...

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

.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). 🚀⚙️

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

github.com/dotnet/core/...

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

.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.

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

Yes, should be in .NET 10 Preview 6

And soon just
dotnet app.cs
😎

github.com/dotnet/sdk/p...

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.

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...

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

Old version using Bootstrap

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