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Agent skill

Csharp Idioms

by irahardianto in irahardianto/awesome-agv

Modern C (10+/.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI.

MITAuto-check passedDevelopment

Install Csharp Idioms

skills CLI
$ npx skills add irahardianto/awesome-agv --skill csharp-idioms -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install irahardianto/awesome-agv csharp-idioms --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/irahardianto/awesome-agv.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/csharp-idioms .claude/skills/csharp-idioms && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
csharp-idioms
GitHub stars
157
Token cost
~1.3k tokens
SKILL.md length
258 words
Files
1
Skills in repo
34
Repo updated
First seen
Licence
MIT

At a glance

Modern C (10+/.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI.

  • Works in 4 steps: Nullable reference types — always enabled → Records for immutable data → Pattern matching → …
  • Reviewing C application code
  • Calls dotnet
  • Tasks that involve Async programming

What it does

Csharp Idioms is an agent skill from irahardianto/awesome-agv. Modern C (10+/.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI. Use when writing, modifying, or reviewing C application code or domain models. Pair with dotnet-idioms for framework APIs.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Async programming. It works with C# and .NET. The repository describes itself as: Comprehensive sets of standards and practices designed to elevate the capabilities of AI coding agents. The licence is MIT.

When your agent uses it

  • Reviewing C application code
  • Tasks that involve Async programming

Example prompts

  • “/csharp-idioms”

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

  1. Nullable reference types — always enabled
  2. Records for immutable data
  3. Pattern matching
  4. required and init for safe construction

What it can do on your machine

Read from SKILL.md and the folder at commit 9e997ba. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • dotnet

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Csharp Idioms loads about 1.3k tokens when it runs. Until then it costs about 72 tokens; SKILL.md has 258 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~72
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from irahardianto/awesome-agv at commit 9e997ba, republished under its MIT licence (© irahardianto). 258 words, ~1,339 tokens.

Download SKILL.mdSave it as .claude/skills/csharp-idioms/SKILL.md (or your agent's skills folder).
name
csharp-idioms
description
Modern C# (10+/.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI. Use when writing, modifying, or reviewing C# application code or domain models. Pair with dotnet-idioms for framework APIs.

C# Idioms and Patterns

C# rewards type safety, LINQ expressiveness, and async-first design. Modern C# (10+/.NET 6+) favors records, nullable reference types, and minimal APIs. Idiomatic C# = clean, async-aware, framework-integrated.

Scope: C# coding idioms. Test naming: .agents/rules/testing-strategy.md. Logging: @.agents/skills/logging-implementation/SKILL.md.

Modern C# Features (10+)

  1. Nullable reference types — always enabled:

    csharp
    // ✅ Explicit nullability
public Task? FindById(string id) { ... }
public Task GetById(string id) { ... } // never returns null — throws

// In .csproj: <Nullable>enable</Nullable>

  2. Records for immutable data:

    csharp
    public record CreateTaskRequest(string Title, Priority Priority);
public record TaskResponse(string Id, string Title, DateTime CreatedAt);

  3. Pattern matching:

    csharp
    return result switch
{
    Success(var task) => Ok(task),
    NotFound(var id) => NotFound($"Task {id} not found"),
    ValidationError(var errors) => BadRequest(errors),
    _ => StatusCode(500)
};

  4. required and init for safe construction:

    csharp
    public class AppConfig
{
    public required string DatabaseUrl { get; init; }
    public required string ApiKey { get; init; }
    public int MaxRetries { get; init; } = 3;
}
Error Handling

  1. Result pattern over exceptions for expected failures:

    csharp
    public record Result<T>
{
    public T? Value { get; init; }
    public string? Error { get; init; }
    public bool IsSuccess => Error is null;
    public static Result<T> Ok(T value) => new() { Value = value };
    public static Result<T> Fail(string error) => new() { Error = error };
}

  2. Domain exceptions for unexpected failures — never raw Exception.

  3. Never catch (Exception) without re-throw or specific handling.

Async/Await

  1. Async all the way — never .Result or .Wait() on tasks:

    csharp
    // ✅ Async pipeline
public async Task<Task> GetTaskAsync(string id, CancellationToken ct)
{
    return await _storage.GetByIdAsync(id, ct)
        ?? throw new NotFoundException("Task", id);
}

// ❌ Sync-over-async — deadlock risk
var task = _storage.GetByIdAsync(id).Result;

  2. Always accept CancellationToken on async methods.

  3. ConfigureAwait(false) in library code only.

Dependency Injection

  1. Constructor injection — no property or method injection:

    csharp
    public class TaskService
{
    private readonly ITaskStorage _storage;
    private readonly ILogger<TaskService> _logger;

    public TaskService(ITaskStorage storage, ILogger<TaskService> logger)
    {
        _storage = storage;
        _logger = logger;
    }
}

  2. Register in DI container — never new a service:

    csharp
    builder.Services.AddScoped<ITaskStorage, PostgresTaskStorage>();
builder.Services.AddScoped<TaskService>();
Show full SKILL.md (163 more words)Show less
LINQ

  1. Prefer method syntax for complex queries, query syntax for joins:

    csharp
    var active = tasks
    .Where(t => t.IsActive)
    .OrderByDescending(t => t.Priority)
    .Select(t => new TaskSummary(t.Id, t.Title));

  2. Never mutate collections during LINQ iteration.

Naming
  1. PascalCase for classes, methods, properties, events, namespaces.
  2. camelCase for parameters, local variables.
  3. _camelCase for private fields (prefix underscore).
  4. I prefix for interfaces: ITaskStorage.
  5. Async suffix for async methods: GetByIdAsync.
Testing

  1. xUnit + FluentAssertions:

    csharp
    [Fact]
public async Task GetTask_ReturnsTask_WhenExists()
{
    var result = await _service.GetTaskAsync("task-1", CancellationToken.None);
    result.Should().NotBeNull();
    result.Title.Should().Be("Test Task");
}

  2. [Theory] for parameterized tests:

    csharp
    [Theory]
[InlineData("low", 1)]
[InlineData("medium", 5)]
[InlineData("high", 10)]
public void PriorityScore_MapsCorrectly(string priority, int expected)
{
    Priority.Score(priority).Should().Be(expected);
}

  3. NSubstitute or Moq for mocking.

Formatting and Static Analysis
ToolPurposeCommand
dotnet formatCanonical formattingdotnet format
Roslyn AnalyzersCompile-time analysisBuilt-in
SonarAnalyzerComprehensive analysisNuGet package
dotnet-outdatedDependency freshnessdotnet-outdated
dotnet list package --vulnerableCVE scanningBuilt-in (.NET 8+)
  • Code Idioms and Conventions .agents/rules/code-idioms-and-conventions.md
  • Testing Strategy .agents/rules/testing-strategy.md
  • Error Handling Principles .agents/rules/error-handling-principles.md
  • Dependency Management Principles @.agents/rules/dependency-management-principles.md

© irahardianto, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/csharp-idioms of irahardianto/awesome-agv.

Open the folder on GitHubat commit 9e997ba

Compare with similar skills

Csharp Idioms next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Csharp Idioms compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Csharp Idioms this skillirahardianto/awesome-agv157—~1.3kAutomated safety check: PassMIT
Akka.NET Best PracticesAaronontheweb/dotnet-skills1.2k1 repos~3.3kAutomated safety check: PassMIT
Dotnet Csharpnovotnyllc/dotnet-artisan233—~1.7kAutomated safety check: PassMIT
Csharp Concurrency PatternsAaronontheweb/dotnet-skills1.2k1 repos~2.2kAutomated safety check: PassMIT
Csharp Prodavila7/claude-code-templates32k8 repos~538Automated safety check: PassMIT
Dotnet Patternsaffaan-m/ECC276k1 repos~2.3kAutomated safety check: PassMIT

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Works with

Categories

Questions about Csharp Idioms

What does Csharp Idioms do?

Modern C (10+/.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI. Csharp Idioms is an agent skill from irahardianto/awesome-agv.NET) coding idioms: nullable reference types, records, pattern matching, async/await with CancellationTokens, LINQ performance, and DI.

When should I use Csharp Idioms?

Csharp Idioms fits situations like: reviewing C application code; tasks that involve Async programming.

How do I install Csharp Idioms in Claude Code?

Run `npx skills add irahardianto/awesome-agv --skill csharp-idioms -a claude-code`. Or copy the skill folder (.agents/skills/csharp-idioms in irahardianto/awesome-agv) into .claude/skills/csharp-idioms in your project. Claude Code loads it when a task matches its description.

How do I install Csharp Idioms in Codex?

Run `npx skills add irahardianto/awesome-agv --skill csharp-idioms -a codex`. Or copy the skill folder (.agents/skills/csharp-idioms in irahardianto/awesome-agv) into .agents/skills/csharp-idioms in your project. Codex loads it when a task matches its description.

Can I use Csharp Idioms in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add irahardianto/awesome-agv --skill csharp-idioms -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/csharp-idioms, .gemini/skills/csharp-idioms, .github/skills/csharp-idioms and .opencode/skills/csharp-idioms in your project.

What does Csharp Idioms need to run?

Going by SKILL.md and its folder, Csharp Idioms needs the command-line tools its instructions call (dotnet).

Does Csharp Idioms access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Csharp Idioms safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Csharp Idioms use?

Csharp Idioms is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Csharp Idioms use?

About 1.3k tokens (SKILL.md is roughly 5.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Csharp Idioms?

Skills that share tags, products or a category with Csharp Idioms: Akka.NET Best Practices (Aaronontheweb/dotnet-skills, 1.2k stars), Dotnet Csharp (novotnyllc/dotnet-artisan, 233 stars), Csharp Concurrency Patterns (Aaronontheweb/dotnet-skills, 1.2k stars) and Csharp Pro (davila7/claude-code-templates, 32k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Csharp Idioms?

irahardianto (a GitHub user) maintains it in irahardianto/awesome-agv, which has 157 GitHub stars. The repository holds 34 skills in this directory. The repository was last updated on October 5, 2026.

Source: irahardianto/awesome-agv on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.