ClrKernel Notebooks

Run C# notebooks in VS Code on ClrKernel — no Python, no Jupyter.

Files matching *.nb.md open as notebooks: fenced ```csharp blocks are code cells, everything else is markdown. The same file is a readable document on GitHub and runs headlessly in any ClrKernel session via #!import — one file, three lives.

Features

Real C# with REPL state — variables, classes, and usings persist across cells, powered by Roslyn scripting (the same engine as the ClrKernel Jupyter kernel).
IntelliSense that knows your session — completion, hover, and signature help from a built-in language server (no C# Dev Kit needed). Completions reflect the live session: variables from cells you've run, types from #r "nuget:" packages, and your imports.
NuGet packages in cells — #r "nuget: PackageName, Version", plus custom feeds via #i "nuget:<feed-url>".
Shared libraries — #!import "lib.dib" / #!lib with --register prefixes and run-once semantics; imports .dib, .ipynb, .md, and .csx files.
Live output — Console.WriteLine streams as it happens; displays created with DisplayAs update in place (progress, timers, tables).
Executable markdown — notebooks that render as plain markdown everywhere else and diff cleanly in pull requests.

Quick start

Install the .NET SDK (8.0 or later).
Install this extension.
Run a cell. The first time, if ClrKernel isn't found the extension offers to install it for you (dotnet tool install --global ClrKernel). Prefer to do it yourself? Run that command in a terminal ahead of time.
Create a notebook — either run ClrKernel: New Markdown Notebook from the Command Palette (or File → New File… → Markdown Notebook), or make a file ending in .nb.md:
```
# My first ClrKernel notebook

```csharp
Console.WriteLine("Hello from ClrKernel");
```
```
Run the cell with the ClrKernel C# controller.

.nb.md files open as notebooks automatically. If one opens as plain text instead (a pre-existing editor association can win), right-click it → Reopen Editor With… → ClrKernel Markdown Notebook, or add "workbench.editorAssociations": { "*.nb.md": "clrkernel-markdown" } to your settings.

Settings

Setting	Default	Description
`clrkernel.server.command`	`clrkernel`	Command that launches the server. The default works when the `ClrKernel` global dotnet tool is installed.
`clrkernel.server.args`	`["lsp"]`	Arguments for the command. For a dev build, set command to `dotnet` and args to `["<path>/ClrKernel.dll", "lsp"]`.

The server's log (including anything it writes to stderr) is in the ClrKernel output channel (View → Output).

How it works

The extension spawns clrkernel lsp — a Language Server over stdio — and talks to it with a single connection that carries both cell execution and the language features (completion, hover, signature help). Because execution and IntelliSense share one process and one ClrKernel.Core engine, completions reflect exactly what you've run. One server runs per VS Code window; REPL state is shared across notebooks in that window, like a Jupyter kernel session.

Requirements

.NET runtime 8.0+ (newer majors work)
ClrKernel on PATH (dotnet tool) or configured via settings

Developing this extension

dotnet build src/ClrKernel/ClrKernel.csproj -c Release
cd editors/vscode
npm install
npm run compile

Open editors/vscode in VS Code and press F5 — the Extension Development Host launches with samples/ open. Point the settings at your built ClrKernel.dll (command dotnet, args [<path-to-dll>, "lsp"]).

License

Apache-2.0