build-csharp-project

build-csharp-project is a skill for Claude Code, Codex from gaelic-ghost/socket. It costs 37 tokens per session (969 once invoked), scanned A, original, Apache-2.0.

A guide for building or changing C# projects on .NET with nullable-aware code, clear types, asynchronous operations, analyzer rules, and focused tests.

In plain words
What is it for?
Use it to modify C# libraries, applications, APIs, hosts, tests, or code shared with other .NET projects.
Why use it?
It helps new code fit the existing C# project and avoids common problems around null values, async behavior, style checks, and untested changes.

Skill for Claude CodeCodex

Part of the dotnet-skills plugin — 12 skills shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/gaelic-ghost/socket/build-csharp-project
Any agent
npx skills add gaelic-ghost/socket --skill build-csharp-project
Clone the repo
git clone --depth 1 https://github.com/gaelic-ghost/socket

Made for: Claude Code, Codex.

Or install dotnet-skills, the plugin that ships this one along with the rest of its 12 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for build-csharp-project

README.md
[![agentmods](https://agentmods.dev/badge/skills/gaelic-ghost/socket/build-csharp-project.svg)](https://agentmods.dev/skills/gaelic-ghost/socket/build-csharp-project)
Your own site
<a href="https://agentmods.dev/skills/gaelic-ghost/socket/build-csharp-project"><img src="https://agentmods.dev/badge/skills/gaelic-ghost/socket/build-csharp-project.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 969 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00037 $0.00969
Opus 5 $0.00018 $0.00485
Sonnet 5 $0.00007 $0.00194
Haiku 4.5 $0.00004 $0.00097

Measured yesterday against content hash abad2529ad71, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

build-csharp-project scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/dotnet-skills/skills/build-csharp-project/SKILL.md · 108 lines

How it starts

The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Build C# Project

Purpose

Implement or modify a C# .NET project in C#'s own shape while keeping F# as an equal peer elsewhere in the plugin.

The practical goal is clear nullable-aware APIs, focused types, useful async boundaries, tests that cover changed behavior, and validation through the repository's .NET commands.

When To Use

  • Use this skill when the chosen language is C#.
  • Use this skill when an existing .csproj needs new source, tests, or package-facing API.
  • Use this skill when a mixed solution has a C# host, app, API, or interop surface.
  • Use this skill when the user asks for C# implementation specifically.

Source Check

Use repo-local .NET files, checked-out dependency sources, Dash MCP or Dash HTTP for installed .NET docsets, and then official Microsoft documentation when Dash/local coverage is missing or stale:

Inspect the repository before editing:

rg --files -g '*.cs' -g '*.csproj' -g '*.sln' -g '*.slnx' -g 'global.json' -g '.editorconfig'

Implementation Workflow

  1. Read the existing project file and analyzer/style settings.
  2. Check nullable reference type behavior.
  3. Identify the public API or app behavior being changed.
  4. Use records for value-like data when that matches the domain.
  5. Use classes for identity, behavior, mutable state, or framework integration.
  6. Use interfaces only when there is a real alternate implementation, test boundary, or public contract.
  7. Keep async APIs async only when they perform asynchronous work or match an existing contract.
  8. Add or update tests around the behavior changed.
  9. Run the narrowest useful validation command.

Nullable And Analyzer Behavior

Read the full file on GitHub · 108 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 108 lines · 37 tokens per session scan A abad2529ad71

Subscribe to this mod's changes

build-csharp-project is a skill published in the GitHub repository gaelic-ghost/socket (7 stars, last pushed 9d ago), licensed Apache-2.0. It adds 37 tokens to every session and 969 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.