C#

Plugin: @ctxo/lang-csharp (npm) Parser: ctxo-roslyn helper (.NET SDK 8+) with tree-sitter-c-sharp fallback Tier: full (advertised), downgrades to syntax when .NET SDK is missing Extensions: .cs

What this plugin does

The C# plugin wraps a small .NET helper project (tools/ctxo-roslyn) that hosts the Roslyn compiler APIs. At index time the plugin launches the helper as a long-running process, loads the solution or project, and streams per-file index results back over stdio. A composite adapter picks between Roslyn and a tree-sitter fallback at initialize() time so you never have to configure which one is active.

If .NET SDK 8+ is not on PATH, or no .sln / .csproj is found, the plugin downgrades to the tree-sitter syntax adapter. Both adapters produce the same SymbolNode and GraphEdge shapes; only the resolution quality differs.

Install

pnpm

pnpm add -D @ctxo/lang-csharp

npm

npm install --save-dev @ctxo/lang-csharp

yarn

yarn add -D @ctxo/lang-csharp

Or:

npx ctxo install csharp --yes

For full tier, install a .NET SDK 8+ alongside Node.js. The helper project lives inside the installed plugin and is restored on first use.

Roslyn vs tree-sitter

Capability	Roslyn (full)	tree-sitter (syntax)
Symbol extraction	yes	yes
imports edges	yes	yes
Cross-file calls resolution	yes	limited
extends / implements on nominal types	yes	yes
Generic type argument uses edges	yes	no
Extension methods resolved to defining class	yes	no
Partial class merging across files	yes	no
Cyclomatic complexity	yes	yes

Roslyn drives the full tier because it can ask the real compiler for the symbol behind every IdentifierNameSyntax, which tree-sitter cannot.

What it extracts

Symbols

Kind	Sources
class	class declarations (partial classes merged in full tier)
interface	interface declarations
method	Methods, constructors, property accessors
function	Local functions, top-level statements
type	struct, record, enum, delegate
variable	Top-level fields and constants

Edges

Kind	Notes
imports	using directives
calls	Method invocations; resolved against the IMethodSymbol in full tier
extends	Base class in : Base clauses
implements	Interfaces in the same base list
uses	Type references in fields, parameters, generic arguments, attributes

Solution (.sln) discovery

Roslyn needs a project or solution to open. The plugin probes the project root for the first match:

1. Any *.sln file in the root
2. Any *.csproj file in the root

If neither is found, Roslyn logs Roslyn adapter unavailable: no .sln or .csproj found and the tree-sitter fallback takes over. For nested layouts, keep a solution file at the ctxo project root, or run ctxo index from the directory that contains the .sln.

Known issues

• Cold start: the first Roslyn run restores NuGet packages for ctxo-roslyn and warms up MSBuild. Subsequent runs are much faster thanks to the keep-alive process used by ctxo watch.
• Source generators: generated files in obj/Generated are indexed like any other .cs file. If you do not want them in the graph, add obj/** to .ctxo/config.yaml#index.ignore.
• Scripting files (.csx) are not supported.

Related

• Dependency graph
• Symbol IDs
• Edge kinds
• Languages overview