Master C#/.NET backend development patterns for building robust APIs, MCP servers, and enterprise applications. Covers async/await, dependency injection, Entity Framework Core, Dapper, configuration, caching, and testing with xUnit. Use when developing .NET backends, reviewing C# code, or designing

.NET Backend Development Patterns Master C /.NET patterns for building production grade APIs, MCP servers, and enterprise backends with modern best practices (2024/2025). When to Use This Skill Developing new .NET Web APIs or MCP servers Reviewing C code for quality and performance Designing service architectures with dependency injection Implementing caching strategies with Redis Writing unit and integration tests Optimizing database access with EF Core or Dapper Configuring applications with IOptions pattern Handling errors and implementing resilience patterns Core Concepts 1. Project Structure (Clean Architecture) 2. Dependency Injection Patterns 3. Async/Await Patterns 4. Configuration with IOptions 5. Result Pattern (Avoiding Exceptions for Flow Control) Data Access Patterns Entity Framework Core Dapper for Performance Caching Patterns Multi Level Cache with Redis Testing Patterns Unit Tests with xUnit and Moq Integration Tests with WebApplicationFactory Best Practices DO 1. Use async/await all the way through the call stack 2. Inject dependencies through constructor injection 3. Use IOptions<T for typed configuration 4. Return Result types instead of throwing exceptions for business logic 5. Use CancellationToken in all async methods 6. Prefer Dapper for read heavy, performance critical queries 7. Use EF Core for complex domain models with change tracking 8. Cache aggressively with proper invalidation strategies 9. Write unit tests for business logic, integration tests for APIs 10. Use record types for DTOs and immutable data DON'T 1. Don't block on async with .Result or .Wait() 2. Don't use async void except for event handlers 3. Don't catch generic Exception without re throwing or logging 4. Don't hardcode configuration values 5. Don't expose EF entities directly in APIs (use DTOs) 6. Don't forget AsNoTracking() for read only queries 7. Don't ignore CancellationToken parameters 8. Don't create new HttpClient() manually (use IHttpClientFactory) 9. Don't mix sync and async code unnecessarily 10. Don't skip validation at API boundaries Common Pitfalls N+1 Queries : Use .Include() or explicit joins Memory Leaks : Dispose IDisposable resources, use using Deadlocks : Don't mix sync and async, use ConfigureAwait(false) in libraries Over fetching : Select only needed columns, use projections Missing Indexes : Check query plans, add indexes for common filters Timeout Issues : Configure appropriate timeouts for HTTP clients Cache Stampede : Use distributed locks for cache population

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