csharp-dotnet

csharp-dotnet is a skill for Claude Code, Codex from nimadorostkar/Claude-Skills-collection. It costs 44 tokens per session (838 once invoked), scanned A, original, MIT.

A guide for building C# applications on .NET 8 and later, including web APIs, background services, and database access with Entity Framework Core.

In plain words
What is it for?
Use it when writing or reviewing modern C# code, designing ASP.NET Core APIs, fixing async problems, or improving Entity Framework Core queries.
Why use it?
It helps prevent null-related bugs, incorrect asynchronous code, dependency-injection mistakes, and database queries that do far more work than expected.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when writing or reviewing modern C# code, designing ASP.NET Core APIs, fixing async problems, or improving Entity Framework Core queries.

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Install with agentmods
npx agentmods add skills/nimadorostkar/claude-skills-collection/csharp-dotnet
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 nimadorostkar/Claude-Skills-collection --skill csharp-dotnet
Clone the repo
git clone --depth 1 https://github.com/nimadorostkar/Claude-Skills-collection

Made for: Claude Code, 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 csharp-dotnet

README.md
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Your own site
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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 csharp-dotnet

Your own site · 80×15
<a href="https://agentmods.dev/skills/nimadorostkar/claude-skills-collection/csharp-dotnet"><img src="https://agentmods.dev/badge/skills/nimadorostkar/claude-skills-collection/csharp-dotnet.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 838 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 pass 7 Sept 2026
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 $0.00044 $0.00838
Opus 5 $0.00022 $0.00419
Sonnet 5 $0.00009 $0.00168
Haiku 4.5 $0.00004 $0.00084

Measured 7d ago against content hash fcecb2e61c88, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

csharp-dotnet 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 7d ago.

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.

skills/languages/csharp-dotnet/SKILL.md · 92 lines

How it starts

The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.

C# and .NET

Purpose

Build .NET applications that are null-safe by contract, correctly asynchronous end to end, and free of the ORM traps that quietly turn one query into a thousand.

When to Use

  • Writing or reviewing C# on .NET 8 or later.
  • Enabling nullable reference types on an existing project.
  • Designing minimal APIs or ASP.NET Core services.
  • Diagnosing async deadlocks or thread-pool starvation.
  • Fixing EF Core N+1 queries and tracking overhead.

Capabilities

  • Nullable reference types, records, pattern matching, required members.
  • Async correctness: ConfigureAwait, cancellation tokens, IAsyncEnumerable.
  • Minimal APIs, endpoint filters, model validation, problem details.
  • Dependency injection lifetimes and scope correctness.
  • EF Core: projections, split queries, no-tracking reads, compiled queries.

Inputs

  • Solution or project files and target framework.
  • Whether the project is a library, web API, or worker service.
  • Data-access layer and database engine.

Outputs

  • Code compiling with <Nullable>enable</Nullable> and <TreatWarningsAsErrors>true</TreatWarningsAsErrors>.
  • Async paths that flow a CancellationToken from request to database.
  • EF Core queries with explicit projection and tracking behavior.

Workflow

  1. Enable the gates — Nullable reference types and warnings-as-errors, project-wide.
  2. Model — Records for immutable values; required members instead of constructor sprawl.
  3. Thread cancellation — Every async method takes a CancellationToken and passes it down.
  4. Shape the queries — Project to DTOs; never materialize entities you will not mutate.
  5. Gate — Build with warnings as errors, run analyzers, run the test suite.

Best Practices

  • Never call .Result or .Wait() on a Task. That is how deadlocks and starvation happen — async all the way down.
  • Use ConfigureAwait(false) in library code; it is unnecessary in ASP.NET Core application code.
  • Register DbContext as scoped. Injecting it into a singleton is a correctness bug, not a style issue.
  • Read-only queries use AsNoTracking(). Tracking every row you only intend to display wastes memory and time.
  • Return Results.Problem(...) / RFC 7807 payloads rather than bare status codes.
  • Validate at the endpoint, not in the domain. The domain should be able to assume its inputs are valid.

Read the full file on GitHub · 92 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. 7d ago First seen · 92 lines · 44 tokens per session scan A fcecb2e61c88

Subscribe to this mod's changes

csharp-dotnet is a skill published in the GitHub repository nimadorostkar/Claude-Skills-collection (26 stars, last pushed 23d ago), licensed MIT. It adds 44 tokens to every session and 838 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.

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