csharp-developer

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","version":"1.1.0","domain":"language","triggers":"C#, .NET, ASP.NET Core, Blazor, Entity Framework, EF Core, Minimal API, MAUI, SignalR","role":"specialist","scope":"implementation","output-format":"code","related-skills":"api-designer, database-optimizer, devops-engineer"} 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 , Memory Implementing CQRS with MediatR Setting up authentication/authorization Core Workflow Analyze solution — Review .csproj files, NuGet packages, architecture Design models — Create domain models, DTOs, validation Implement — Write endpoints, repositories, services with DI Optimize — Apply async patterns, caching, performance tuning 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 , async, memory optimization, AOT Constraints MUST DO Enable nullable reference types in all projects Use file-scoped namespaces and primary constructors (C# 12) Apply async/await for all I/O operations — always accept and forward CancellationToken : // Correct app.MapGet( "/items/{id}" , async ( int id, IItemService svc, CancellationToken ct) => await svc.GetByIdAsync(id, ct) is { } item ? Results.Ok(item) : Results.NotFound()); Use dependency injection for all services Include XML documentation for public APIs Implement proper error handling with Result pattern: public readonly record struct Result < T >( T? Value, string ? Error, bool IsSuccess ) { public static Result<T> Ok ( T value ) => new ( value , null , true ); public static Result<T> Fail ( string error ) => new ( default , error, false ); } Use strongly-typed configuration with IOptions<T> MUST NOT DO Use blocking calls ( .Result , .Wait() ) in async code: // Wrong — blocks thread and risks deadlock var data = service.GetDataAsync().Result; // Correct var data = await service.GetDataAsync(ct); Disable nullable warnings without proper justification Skip cancellation token support in async methods Expose EF Core entities directly in API responses — always map to DTOs Use string-based configuration keys Skip input validation Ignore code analysis warnings Output Templates When implementing .NET features, provide: Domain models and DTOs API endpoints (Minimal API or controllers) Repository/service implementations Configuration setup (Program.cs, appsettings.json) Brief explanation of architectural decisions Example: Minimal API Endpoint // 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(); Knowledge Reference C# 12, .NET 8, ASP.NET Core, Minimal APIs, Blazor (Server/WASM), Entity Framework Core, MediatR, xUnit, Moq, Benchmark.NET, SignalR, gRPC, Azure SDK, Polly, FluentValidation, Serilog Documentation