n8n-nodes-csharp — C# Code node for n8n

Run custom C# scripts inside n8n workflows, similar to n8n’s built-in Code nodes.

Package: https://www.npmjs.com/package/@madoere/n8n-nodes-csharp

Install (recommended: n8n UI)

In n8n:

1. Go to Settings → Community nodes
2. Choose Install and enter:

@madoere/n8n-nodes-csharp

3. Restart n8n if prompted

If your n8n deployment disables community nodes, enable them using n8n’s docs:

https://docs.n8n.io/integrations/community-nodes/

Using the C# Code node

The node supports two execution modes:

• All Items: run once; use Items
• Per Item: run once per input item; use Item + Index

Return shapes:

• return an object → one output item
• return an array of objects → multiple output items
• return a scalar → wrapped as { "value": ... }

Logging:

• The runner’s stdout is reserved for the JSON response.
• Write logs with Console.Error.WriteLine(...).

Convenience helpers are available on JSON nodes:

• node.Str("field") → string?
• node.Int("field") → int?
• node.Bool("field") → bool?

Example: read name from each incoming item and emit a message:

return Items!.Select(i => new {
    message = i.Str("name") + " from C#",
}).ToArray();

Example: per-item mode (one output per input item):

return new {
    index = Index,
    message = Item.Str("name") + " from C#",
};

Custom // using ... directives (including System.Text)

You can add namespace imports by placing special header comments at the top of your script:

// using System.Text
// using global::System.Net

var sb = new StringBuilder();
sb.Append("hello");
return new { text = sb.ToString() };

Rules (simplified):

• Only namespace imports are supported (no static, no aliases).
• The runner scans only the initial header region and stops at the first non-empty, non-comment line.
• Invalid // using ... syntax fails the node with a readable error.

Runner / runtime

This node executes C# in a separate runner process (no in-process CLR hosting).

• By default, the node uses a runner shipped inside the npm package.
• On Linux x64/arm64, it auto-detects glibc vs musl and selects the matching self-contained runner.
• On other platforms, build/provide your own runner and set N8N_CSHARP_RUNNER_PATH.
  • If you point to a .dll, the runtime must have dotnet available on PATH.

Security / sandboxing

This node executes user-provided C# code with no sandboxing.

Treat access to this node as equivalent to granting arbitrary code execution on the machine/container running n8n:

• The script can read/write files accessible to the n8n process, call the network, and consume CPU/memory.
• There are no built-in isolation guarantees, permissions, or resource limits beyond what your OS/container provides.

Only use this node in trusted environments (trusted workflows + trusted users), and rely on external isolation/hardening (separate instance, container/VM boundaries, least-privilege filesystem/networking, etc.).

Documentation

Long-lived project notes live in docs/README.md.

Quick start (Docker)

For local testing/dev, you can build and start n8n with the C# node installed:

docker compose up -d --build

Then open:

http://localhost:5678

What’s in this repo

• n8n-nodes-csharp/ — n8n community node package (TypeScript)
• runner/N8n.CSharpRunner/ — .NET runner (C#) invoked by the node as a separate process

The node owns the n8n UI + framework integration. It executes C# in a separate runner process.

For published releases, the npm package includes self-contained runner executables for Linux (glibc + musl, x64 + arm64), and the node auto-selects the correct one at runtime.

Build locally

1. Publish the runner into the node package:

Release-like (builds all Linux variants into n8n-nodes-csharp/runner/<rid>/):

node scripts/publish-runner-multi-rid.mjs

Or build a single self-contained runner for your target (example for Alpine x64):

dotnet publish runner/N8n.CSharpRunner -c Release -r linux-musl-x64 --self-contained true -o n8n-nodes-csharp/runner/linux-musl-x64

2. Build the node package:

cd n8n-nodes-csharp && npm ci && npm run build

Docker

Example custom image: Dockerfile.n8n-csharp (built on top of n8nio/n8n:latest)

Build the image directly:

docker build -f Dockerfile.n8n-csharp -t n8n-csharp-local:dev .

Or run via compose:

docker compose up -d --build

Notes:

• n8nio/n8n:latest is Alpine-based; the Dockerfile uses a self-contained Linux/musl runner and runs it in globalization-invariant mode.

License

MIT (see LICENSE).