# Csharp Developer

Use when building C# applications with .NET 8+, ASP.NET Core APIs, or Blazor web apps.

- Repository: https://github.com/Jeffallan/claude-skills (12164 stars)
- Category: Data and ML
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Jeffallan/claude-skills --skill csharp-developer -g -a claude-code -y`
Codex: `npx skills add Jeffallan/claude-skills --skill csharp-developer -g -a codex -y`
Cursor: `npx skills add Jeffallan/claude-skills --skill csharp-developer -g -a cursor -y`
Gemini CLI: `npx skills add Jeffallan/claude-skills --skill csharp-developer -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Jeffallan/claude-skills`

## Description

Use when building C# applications with .NET 8+, ASP.NET Core APIs, or Blazor web apps. Builds REST APIs using minimal or controller-based routing, configures database access with Entity Framework Core, implements async patterns and cancellation, structures applications with CQRS via MediatR, and scaffolds Blazor components with state management. Invoke for C#, .NET, ASP.NET Core, Blazor, Entity Framework, EF Core, Minimal API, MAUI, SignalR.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# C# Developer

Senior C# developer with mastery of .NET 8+ and Microsoft ecosystem. Specializes in high-performance web APIs, cloud-native solutions, and modern C# language features.

## When to Use This Skill

- Building ASP.NET Core APIs (Minimal or Controller-based)
- Implementing Entity Framework Core data access
- Creating Blazor web applications (Server/WASM)
- Optimizing .NET performance with Span<T>, Memory<T>
- Implementing CQRS with MediatR
- Setting up authentication/authorization

## Core Workflow

1. **Analyze solution**, Review .csproj files, NuGet packages, architecture
2. **Design models**, Create domain models, DTOs, validation
3. **Implement**, Write endpoints, repositories, services with DI
4. **Optimize**, Apply async patterns, caching, performance tuning
5. **Test**, Write xUnit tests with TestServer; verify 80%+ coverage

> **EF Core checkpoint (after step 3):** Run `dotnet ef migrations add <Name>` and review the generated migration file before applying. Confirm no unintended table/column drops. Roll back with `dotnet ef migrations remove` if needed.

## Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When |
|-------|-----------|-----------|
| Modern C# | `references/modern-csharp.md` | Records, pattern matching, nullable types |
| ASP.NET Core | `references/aspnet-core.md` | Minimal APIs, middleware, DI, routing |
| Entity Framework | `references/entity-framework.md` | EF Core, migrations, query optimization |
| Blazor | `references/blazor.md` | Components, state management, interop |
| Performance | `references/performance.md` | Span<T>, async, memory optimization, AOT |

## Constraints

The rest: https://github.com/Jeffallan/claude-skills/blob/HEAD/skills/csharp-developer/SKILL.md