C# and .NET Developer

What it does

When your agent uses it

• Building a minimal or controller-based ASP.NET Core API
• Adding Entity Framework Core data access and reviewing its migrations
• Creating Blazor Server or WebAssembly components with state management
• Structuring commands and queries with CQRS and MediatR

Example prompts

• “Build a minimal API for managing inventory items with EF Core and cancellation tokens.”
• “Add a Blazor Server component that lists orders and keeps its own state.”
• “Review the migration that dotnet ef just generated for accidental column drops.”
• “Refactor the order handlers into CQRS commands and queries with MediatR.”

Requirements

• The .NET 8 or later SDK
• The dotnet ef tool for migrations

Workflow steps

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

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

What it can do on your machine

Read from SKILL.md and the folder at commit 1be15d8. 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

  Links to these hosts (documentation or services it may open):

  • github.com
  • synergetic.solutions
  • jeffallan.github.io

  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

C# and .NET Developer loads about 1.3k tokens when it runs, and up to ~15k if it reads all its reference files. Until then it costs about 116 tokens; SKILL.md has 361 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~116

When it runs · the whole SKILL.md, loaded when a task matches

~1.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~15k

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

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 Jeffallan/claude-skills at commit 1be15d8, republished under its MIT licence (© Jeffallan). 361 words, ~1,310 tokens.

name

csharp-developer

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.

license

MIT

metadata.author

https://github.com/Jeffallan

metadata.company

https://synergetic.solutions

metadata.version

1.1.0

metadata.domain

language

metadata.triggers

C#, .NET, ASP.NET Core, Blazor, Entity Framework, EF Core, Minimal API, MAUI, SignalR

metadata.role

specialist

metadata.scope

implementation

metadata.output-format

code

metadata.related-skills

api-designer, database-optimizer, devops-engineer

// Program.cs (file-scoped, .NET 8 minimal API)
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddScoped<IProductService, ProductService>();

var app = builder.Build();

app.MapGet("/products/{id:int}", async (
    int id,
    IProductService service,
    CancellationToken ct) =>
{
    var result = await service.GetByIdAsync(id, ct);
    return result.IsSuccess ? Results.Ok(result.Value) : Results.NotFound(result.Error);
})
.WithName("GetProduct")
.Produces<ProductDto>()
.ProducesProblem(404);

app.Run();

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

Files

SKILL.md and 5 other files (references) in skills/csharp-developer of Jeffallan/claude-skills.

• SKILL.md
• references/aspnet-core.md
• references/blazor.md
• references/entity-framework.md
• references/modern-csharp.md
• references/performance.md

Open the folder on GitHubat commit 1be15d8