ClrKernel 0.4.1

ClrKernel

A Jupyter kernel for .NET. C# cells are evaluated with Roslyn's scripting engine (Microsoft.CodeAnalysis.CSharp.Scripting), with more CLR languages (PowerShell, F#) on the roadmap. Notebooks run interactively in JupyterLab / VS Code (Jupyter extension) and headlessly via nbconvert or papermill — including from schedulers like SQL Server Agent.

ClrKernel is a maintained fork of SciSharp/ICSharpCore, created after Microsoft deprecated .NET Interactive / Polyglot Notebooks (April 2026). Relative to upstream it adds: correct headless execution under nbclient/papermill, full output capture for async/await cells, control channel + heartbeat + graceful shutdown_request handling, patched vulnerable dependencies, and the kernelspec shipped inside the NuGet package.

Install

dotnet tool install --global ClrKernel
jupyter kernelspec install "$(clrkernel --kernel-spec-path)" --user --name clrkernel
jupyter kernelspec list   # should show: clrkernel

Requires a .NET 8+ runtime (RollForward=Major: newer majors work) and Jupyter.

Use

Pick the ClrKernel (C#) kernel in JupyterLab or VS Code. Cells support #r "nuget: Package, Version" and #r "path/to/local.dll" references, with REPL-style state persisting across cells.

Importing shared libraries

#!import loads C# code from another file into the session — use it to share helper libraries between notebooks, no .NET Interactive required:

#!import "../lib/jobbooks.dib"

Supports .dib (C# sections run; markdown and other-language sections are skipped), .ipynb (code cells run), and .csx/.cs (whole file). Relative paths resolve against the notebook's directory, and nested #!imports inside a library resolve relative to that library's own file. Each resolved file runs once per session — re-importing is a no-op unless you pass --force (#!import --force "lib.dib"), which is handy while iterating on the library itself. Imported files can use #r directives, including #r "nuget: ...", and can #!import further files.

Headless / scheduled execution:

jupyter nbconvert --to notebook --execute --output out.ipynb etl.ipynb
papermill etl.ipynb runs/etl_out.ipynb -k clrkernel --language .net-csharp -p run_date 2026-08-04

A failing cell exits non-zero (job schedulers see the failure); papermill also persists the partially-executed output notebook as a diagnostic artifact.

Develop

./scripts/install-dev-kernel.sh    # kernel 'clrkernel-dev' running from bin/ output
                                   # iterate: dotnet build + restart kernel
./scripts/install-local-tool.sh    # pack + install the global tool from a local
                                   # feed; tests the full packaged experience
clrkernel --kernel-spec-details    # show which kernelspec the binary resolves

License

Apache 2.0, preserving the upstream license. Original work © SciSharp (Kerry Jiang, Haiping Chen, and contributors); fork maintained by ClrKernel.