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csharp-developer

An agent skill by Jeffallan, from Jeffallan/claude-skills. Tags: api, automation, dotnet, mobile, react, web.

What it does

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.

Install

With the skills CLI, which installs into Claude Code, Codex, Cursor and other agents:

npx skills add Jeffallan/claude-skills --skill csharp-developer

Or copy the skill folder into Claude Code's skills directory by hand (~/.claude/skills for every project, or .claude/skills inside one):

git clone --depth 1 https://github.com/Jeffallan/claude-skills
cp -r claude-skills/skills/csharp-developer ~/.claude/skills/csharp-developer

Safety box score

Grade B, low risk: 19 of 100 risk points, rated 2026-09-22. The grade rates what the skill and its scripts can reach on the machine of whoever installs it, across eight categories from shell execution to secrets access. How the score works.

This skill is a C#/.NET implementation guide that steers the agent to edit project code, configuration, and EF Core migrations. Its main blast-radius risks are local command execution, database schema changes, and a few examples that place secret-bearing settings in app config.

Category levels, from 0 (none) to 3 (high)
CategoryLevelWhy
Code & shell execution1 (low)It explicitly tells the agent to run local tooling such as `dotnet ef migrations add <Name>`, `dotnet ef database update`, `dotnet ef migrations script`, and `BenchmarkRunner.Run<StringBenchmarks>()`, but it ships no shell scripts or native binaries.
Network access0 (none)The skill describes network-enabled app patterns (HTTP, SignalR, JS interop) but does not itself download from or send data to remote hosts.
Filesystem reach1 (low)It expects edits to project files like `Program.cs`, `.csproj`, `appsettings.json`, and generated migration files, but stays within the workspace rather than system paths.
Secrets & credentials1 (low)The ASP.NET Core example puts `JwtSettings.Secret` in `appsettings.json` and reads it with `builder.Configuration.GetSection("JwtSettings").Get<JwtSettings>()!`, which can encourage storing secrets in tracked config.
Privilege & persistence0 (none)There is no use of sudo, service registration, shell/profile editing, or other privilege-changing operations.
Instruction hijack surface0 (none)The files contain normal instructional content only; there are no prompts to ignore higher-priority instructions, hide content, or follow fetched remote instructions.
Irreversible actions2 (moderate)It includes schema-changing database actions such as `dotnet ef database update` and `context.Database.MigrateAsync()`, which can alter or damage data if applied without review.
Transparency0 (none)All shipped files are readable markdown; there are no binaries, minified blobs, or decoded-at-runtime payloads.

Before installing

Rated 2026-09-22 by an automated review of 6 files from the skill's repository.

Source

Repository
Jeffallan/claude-skills (all skills from this repository)
Path
skills/csharp-developer/SKILL.md
Branch
main
Updated
2026-09-19