.NET Lab

^{(aka Razor Lab, formerly also DotNetInternals)}

C# and Razor compiler playground in the browser via Blazor WebAssembly. https://lab.razor.fyi/

C#	Razor

Features

• Razor/CSHTML to generated C# code / IR / Syntax Tree / Errors.
• C# to IL / Syntax / IOperation / Symbols / decompiled-C# / Errors / Execution console output.
• Any Roslyn/Razor compiler version (NuGet official builds or CI builds given PR number / branch / build number).
• Offline support (PWA).
• VSCode Monaco Editor.
• Multiple input sources (especially useful for interlinked Razor components).
• C# Language Services (completions, live diagnostics, code fixes).
• Configuring any C# options (e.g., LangVersion, Features, OptimizationLevel, AllowUnsafe) via Roslyn C# APIs or via #:property directives (both with editor completions).
• Referencing NuGet packages via #:package directives.

Development

The recommended startup app for development is src/Server.

To hit breakpoints, it is recommended to turn off the worker (in app settings).

• eng/BuildTools: build-time tools.
• src/App: the WebAssembly app.
  • cd src/App; dotnet watch - src/Server is better for development though.
• src/Compiler: self-contained project referencing Roslyn/Razor. It's reloaded at runtime with a user-chosen version of Roslyn/Razor. It should be small (for best reloading perf). It can reference shared code which does not depend on Roslyn/Razor from elsewhere (e.g., Shared.csproj).
• src/RazorAccess: internal access to Razor DLLs (via fake assembly name).
• src/RoslynAccess: internal access to Roslyn Compiler DLLs (via fake assembly name).
• src/RoslynCodeStyleAccess: internal access to Roslyn CodeStyle DLLs (via fake assembly name).
• src/RoslynWorkspaceAccess: internal access to Roslyn Workspace DLLs (via fake assembly name).
• src/Server: a Blazor Server entrypoint for easier development of the App (it has better tooling support for hot reload and debugging).
  • cd src/Server; dotnet watch
• src/Shared: code used by Compiler that does not depend on Roslyn/Razor.
• src/Worker: an app loaded in a web worker (a separate process in the browser), so it does all the CPU-intensive work to avoid lagging the user interface.
• src/WorkerApi: shared code between Worker and App. This is in preparation for making the worker independent of the app, so the app can be optimized (trimming, NativeAOT) and the worker can be loaded more lazily.
• test/UnitTests
  • dotnet test

Attribution

• Logo: OpenMoji
• Style: Fluent UI
• Icons: Fluent UI Icons

Related work

Razor REPLs:

• https://blazorrepl.telerik.com/
• https://netcorerepl.telerik.com/
• https://try.mudblazor.com/snippet
• https://blazorfiddle.com/
• https://try.fluentui-blazor.net/snippet

C# REPLs:

• https://dotnetfiddle.net/
• https://onecompiler.com/csharp
• https://www.programiz.com/csharp-programming/online-compiler/

C# compiler playgrounds:

• https://sharplab.io/
• https://godbolt.org/

XAML REPLs:

• https://playground.platform.uno/

Web IDEs:

• https://github.com/Mythetech/Apollo
• https://github.com/Luthetus/Luthetus.Ide
• https://github.com/knervous/intellisage