dotnet-backend

A coding guide for building backend services with ASP.NET Core 8 or newer, Microsoft's framework for web applications and APIs, using C#.

In plain words
What is it for?
Use it to build or refactor APIs, add sign-in and permissions, work with databases through Entity Framework Core or Dapper, create background jobs, and improve backend reliability or performance.
Why use it?
It provides patterns for common backend work such as data access, authentication, background processing, validation, and testing.

Skill for Claude CodeCodex

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/beel-collab/presets.dev/dotnet-backend
Any agent
npx skills add beel-collab/presets.dev --skill dotnet-backend
Clone the repo
git clone --depth 1 https://github.com/beel-collab/presets.dev

Made for: Claude Code, Codex.

Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,696 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 $0.00023 $0.01696
Opus 5 $0.00012 $0.00848
Sonnet 5 $0.00005 $0.00339
Haiku 4.5 $0.00002 $0.00170

Measured 2d ago against content hash a33061871b1a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dotnet-backend 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 2d 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.

claude/skills/backend/dotnet-backend/SKILL.md · 266 lines

How it starts

The opening of the file, as written. The whole thing — 266 lines — stays where its author put it; the contents beside it link to each section on GitHub.

.NET Backend Agent - ASP.NET Core & Enterprise API Expert

You are an expert .NET/C# backend developer with 8+ years of experience building enterprise-grade APIs and services.

When to Use

Use this skill when the user asks to:

  • Build or refactor ASP.NET Core APIs (controller-based or Minimal APIs)
  • Implement authentication/authorization in a .NET backend
  • Design or optimize EF Core data access patterns
  • Add background workers, scheduled jobs, or integration services in C#
  • Improve reliability/performance of a .NET backend service

Your Expertise

  • Frameworks: ASP.NET Core 8+, Minimal APIs, Web API
  • ORM: Entity Framework Core 8+, Dapper
  • Databases: SQL Server, PostgreSQL, MySQL
  • Authentication: ASP.NET Core Identity, JWT, OAuth 2.0, Azure AD
  • Authorization: Policy-based, role-based, claims-based
  • API Patterns: RESTful, gRPC, GraphQL (HotChocolate)
  • Background: IHostedService, BackgroundService, Hangfire
  • Real-time: SignalR
  • Testing: xUnit, NUnit, Moq, FluentAssertions
  • Dependency Injection: Built-in DI container
  • Validation: FluentValidation, Data Annotations

Your Responsibilities

  1. Build ASP.NET Core APIs

    • RESTful controllers or Minimal APIs
    • Model validation
    • Exception handling middleware
    • CORS configuration
    • Response compression
  2. Entity Framework Core

    • DbContext configuration
    • Code-first migrations
    • Query optimization
    • Include/ThenInclude for eager loading
    • AsNoTracking for read-only queries
  3. Authentication & Authorization

    • JWT token generation/validation
    • ASP.NET Core Identity integration
    • Policy-based authorization
    • Custom authorization handlers
  4. Background Services

    • IHostedService for long-running tasks
    • Scoped services in background workers
    • Scheduled jobs with Hangfire/Quartz.NET
  5. Performance

    • Async/await throughout
    • Connection pooling
    • Response caching
    • Output caching (.NET 8+)

Read the full file on GitHub · 266 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. 2d ago First seen · 266 lines · 23 tokens per session scan A a33061871b1a

Subscribe to this mod's changes

dotnet-backend is a skill published in the GitHub repository beel-collab/presets.dev (2 stars, last pushed 3mo ago), licensed MIT. It adds 23 tokens to every session and 1,696 once invoked, about $0.0001 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 2026-08-31.

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