Use when building .NET 8 applications with minimal APIs, clean architecture, or cloud-native microservices. Invoke for Entity Framework Core, CQRS with MediatR, JWT authentication, AOT compilation.
SKILL.md
.NET Core Expert
Core Workflow
Analyze requirements — Identify architecture pattern, data models, API design
Design solution — Create clean architecture layers with proper separation
Implement — Write high-performance code with modern C# features; run dotnet build to verify compilation — if build fails, review errors, fix issues, and rebuild before proceeding
Secure — Add authentication, authorization, and security best practices
Test — Write comprehensive tests with xUnit and integration testing; run dotnet test to confirm all tests pass — if tests fail, diagnose failures, fix the implementation, and re-run before continuing; verify endpoints with curl or a REST client
Reference Guide
Load detailed guidance based on context:
Topic
Reference
Load When
Minimal APIs
references/minimal-apis.md
Creating endpoints, routing, middleware
Clean Architecture
references/clean-architecture.md
CQRS, MediatR, layers, DI patterns
Entity Framework
references/entity-framework.md
DbContext, migrations, relationships
Authentication
references/authentication.md
JWT, Identity, authorization policies
Cloud-Native
references/cloud-native.md
Docker, health checks, configuration
Constraints
MUST DO
Use .NET 8 and C# 12 features
Enable nullable reference types: <Nullable>enable</Nullable> in the .csproj
Use async/await for all I/O operations — e.g., await dbContext.Users.ToListAsync()
Implement proper dependency injection
Use record types for DTOs — e.g., public record UserDto(int Id, string Name);
Follow clean architecture principles
Write integration tests with WebApplicationFactory<Program>
Configure OpenAPI/Swagger documentation
MUST NOT DO
Use synchronous I/O operations
Expose entities directly in API responses
Skip input validation
Use legacy .NET Framework patterns
Mix concerns across architectural layers
Use deprecated EF Core patterns
Code Examples
Minimal API Endpoint
// Program.cs
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddMediatR(cfg => cfg.RegisterServicesFromAssembly(typeof(Program).Assembly));
var app = builder.Build();
app.UseSwagger();
app.UseSwaggerUI();
app.MapGet("/users/{id}", async (int id, ISender sender, CancellationToken ct) =>
{
var result = await sender.Send(new GetUserQuery(id), ct);
return result is null ? Results.NotFound() : Results.Ok(result);
})
.WithName("GetUser")
.Produces<UserDto>()
.ProducesProblem(404);
app.Run();
MediatR Query Handler
// Application/Users/GetUserQuery.cs
public record GetUserQuery(int Id) : IRequest<UserDto?>;
public sealed class GetUserQueryHandler : IRequestHandler<GetUserQuery, UserDto?>
{
private readonly AppDbContext _db;
public GetUserQueryHandler(AppDbContext db) => _db = db;
public async Task<UserDto?> Handle(GetUserQuery request, CancellationToken ct) =>
await _db.Users
.AsNoTracking()
.Where(u => u.Id == request.Id)
.Select(u => new UserDto(u.Id, u.Name))
.FirstOrDefaultAsync(ct);
}
EF Core DbContext with Async Query
// Infrastructure/AppDbContext.cs
public sealed class AppDbContext(DbContextOptions<AppDbContext> options) : DbContext(options)
{
public DbSet<User> Users => Set<User>();
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.ApplyConfigurationsFromAssembly(typeof(AppDbContext).Assembly);
}
}
// Usage in a service
public async Task<IReadOnlyList<UserDto>> GetAllAsync(CancellationToken ct) =>
await _db.Users
.AsNoTracking()
.Select(u => new UserDto(u.Id, u.Name))
.ToListAsync(ct);
DTO with Record Type
public record UserDto(int Id, string Name);
public record CreateUserRequest(string Name, string Email);
