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 sca

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 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 : Use dependency injection for all services Include XML documentation for public APIs Implement proper error handling with Result pattern: Use strongly typed configuration with IOptions<T MUST NOT DO Use blocking calls ( .Result , .Wait() ) in async code: 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: 1. Domain models and DTOs 2. API endpoints (Minimal API or controllers) 3. Repository/service implementations 4. Configuration setup (Program.cs, appsettings.json) 5. Brief explanation of architectural decisions Example: Minimal API Endpoint 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](https://jeffallan.github.io/claude skills/skills/language/csharp developer/)

csharp-developer