dotnet-best-practices

dotnet-best-practices is a skill for Codex from PracticalSwan/agent-skills. It costs 43 tokens per session (1,249 once invoked), scanned A, original, MIT.

A C# and .NET code-review skill for improving maintainability, project structure, asynchronous code, dependency injection, and testability. .NET is Microsoft's platform for building applications, and dependency injection is a way to provide code with the services it needs.

In plain words
What is it for?
It is for reviewing or improving C# code, .NET solution structure, async patterns, service setup, architecture, documentation, and testability.
Why use it?
It gives reviews a defined set of modern conventions for C# projects instead of relying only on general style advice.

Skill for Codex

Written for Codex: reads ~/.codex or $CODEX_HOME. Also seen: mentions Claude Code; mentions Codex.

Good fit It is for reviewing or improving C# code, .NET solution structure, async patterns, service setup, architecture, documentation, and testability.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/practicalswan/agent-skills/dotnet-best-practices
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.

Any agent
npx skills add PracticalSwan/agent-skills --skill dotnet-best-practices
Clone the repo
git clone --depth 1 https://github.com/PracticalSwan/agent-skills

Made for: Codex.

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 dotnet-best-practices

README.md
[![agentmods](https://agentmods.dev/badge/skills/practicalswan/agent-skills/dotnet-best-practices/github.svg)](https://agentmods.dev/skills/practicalswan/agent-skills/dotnet-best-practices)
Your own site
<a href="https://agentmods.dev/skills/practicalswan/agent-skills/dotnet-best-practices"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/dotnet-best-practices/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for dotnet-best-practices

Your own site · 80×15
<a href="https://agentmods.dev/skills/practicalswan/agent-skills/dotnet-best-practices"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/dotnet-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,249 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Prompt Injection · line 142
    Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.
    Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
  • medium Data Exfiltration · line 119
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
How audits are shown
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 5.1 $0.00043 $0.01249
Opus 5 $0.00022 $0.00624
Sonnet 5 $0.00009 $0.00250
Haiku 4.5 $0.00004 $0.00125

Measured yesterday against content hash fa517f4df798, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

dotnet-best-practices 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.

dotnet-best-practices/SKILL.md · 138 lines

How it starts

The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.

.NET/C# Best Practices

Your task is to ensure .NET/C# code in ${selection} meets the best practices specific to this solution/project. This includes:

Documentation & Structure

  • Create comprehensive XML documentation comments for all public classes, interfaces, methods, and properties
  • Include parameter descriptions and return value descriptions in XML comments
  • Follow the established namespace structure: {Core|Console|App|Service}.{Feature}

Design Patterns & Architecture

  • Use primary constructor syntax for dependency injection (e.g., public class MyClass(IDependency dependency))
  • Implement the Command Handler pattern with generic base classes (e.g., CommandHandler<TOptions>)
  • Use interface segregation with clear naming conventions (prefix interfaces with 'I')
  • Follow the Factory pattern for complex object creation.

Dependency Injection & Services

  • Use constructor dependency injection with null checks via ArgumentNullException
  • Register services with appropriate lifetimes (Singleton, Scoped, Transient)
  • Use Microsoft.Extensions.DependencyInjection patterns
  • Implement service interfaces for testability

Resource Management & Localization

  • Use ResourceManager for localized messages and error strings
  • Separate LogMessages and ErrorMessages resource files
  • Access resources via _resourceManager.GetString("MessageKey")

Async/Await Patterns

  • Use async/await for all I/O operations and long-running tasks
  • Return Task or Task from async methods
  • Use ConfigureAwait(false) where appropriate
  • Handle async exceptions properly

Testing Standards

  • Use MSTest framework with FluentAssertions for assertions
  • Follow AAA pattern (Arrange, Act, Assert)
  • Use Moq for mocking dependencies
  • Test both success and failure scenarios
  • Include null parameter validation tests

Configuration & Settings

  • Use strongly-typed configuration classes with data annotations
  • Implement validation attributes (Required, NotEmptyOrWhitespace)
  • Use IConfiguration binding for settings
  • Support appsettings.json configuration files

Read the full file on GitHub · 138 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 Changed · -35 lines fa517f4df798
  2. 2d ago Changed 526387e9b328
  3. 5d ago Changed 8f921da6d2cc
  4. 9d ago First seen · 173 lines · 43 tokens per session scan A d0d90aecd0ee

Subscribe to this mod's changes

dotnet-best-practices is a skill published in the GitHub repository PracticalSwan/agent-skills (13 stars, last pushed yesterday), licensed MIT. It adds 43 tokens to every session and 1,249 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 2026-08-30.

Related

Other skills, from other repositories

author-test

Generate a test given sample. Parameters: C# SDK repository root; Package name: one of Azure.AI.Projects, Azure.AI.Projects.Agents or Azure.AI.Extensions.OpenAI; the sample to use as a starting point for the test.

Azure/azure-sdk-for-net · 68 tokens

migrate-mstest-v3-to-v4

Use this skill before answering, planning, or editing any MSTest 3.x-to-4.x upgrade or post-upgrade failure. Triggers include "MSTest v4 breaking changes"; CS0507/CS0103/CS1061/CS1615; ExecuteAsync, CallerInfo, DisplayName, or custom TestMethodAttribute; ClassCleanupBehavior; ContainsKey; ThrowsExactly or…

managedcode/dotnet-skills · 179 tokens

migrate-xunit-to-mstest

Convert .NET tests from xUnit.net v2/v3 to MSTest v4 while preserving VSTest or MTP. Use for replacing xunit packages, Fact/Theory/InlineData/MemberData, assertions, IClassFixture/ICollectionFixture, ITestOutputHelper, TestContext cancellation, traits/Owner, skips, timeouts, and xUnit parallelization. Also use when a…

managedcode/dotnet-skills · 141 tokens

migrate-xunit-to-xunit-v3

Migrate .NET test projects from xUnit.net v2 to xunit.v3 and fix v3 breaks. Use for package/CPM conversion, OutputType=Exe, preserving the VSTest or MTP runner (including projects currently using YTest.MTP.XUnit2), incompatible TFMs, async void tests, string-to-Type attributes, custom Fact/Theory/BeforeAfterTest…

managedcode/dotnet-skills · 149 tokens

resharper-clt

Use the free official JetBrains ReSharper Command Line Tools for .NET repositories. USE FOR: jb inspectcode; jb cleanupcode; stronger C# inspections, cleanup profiles, and CI-friendly JetBrains analysis. DO NOT USE FOR: replacing tests with inspection output; ad-hoc formatting-only work when the repo intentionally…

managedcode/dotnet-skills · 107 tokens

roslynator

Use the open-source free Roslynator analyzer packages and optional CLI for .NET. USE FOR: Roslynator.Analyzers setup; Roslynator CLI checks or cleanup; C# linting, static analysis, and code-fix automation. DO NOT USE FOR: overlapping analyzer packs with no consolidation plan; formatting-only work owned by another…

managedcode/dotnet-skills · 107 tokens