Instruction file imported from turibbio/agentic-instructions (.github/instructions/csharp.instructions.md). Copyright stays with the author.

C# Development

C# Instructions

• Always use the latest version C#, currently C# 13 features.
• Write clear and concise comments for each function.

General Instructions

• Make only high confidence suggestions when reviewing code changes.
• Write code with good maintainability practices, including comments on why certain design decisions were made.
• Handle edge cases and write clear exception handling.
• For libraries or external dependencies, mention their usage and purpose in comments.

Naming Conventions

• Follow PascalCase for component names, method names, and public members.
• Use camelCase for private fields and local variables.
• Prefix interface names with "I" (e.g., IUserService).

Formatting

• Apply code-formatting style defined in .editorconfig.
• Prefer file-scoped namespace declarations and single-line using directives.
• Insert a newline before the opening curly brace of any code block (e.g., after if, for, while, foreach, using, try, etc.).
• Ensure that the final return statement of a method is on its own line.
• Use pattern matching and switch expressions wherever possible.
• Use nameof instead of string literals when referring to member names.
• Ensure that XML doc comments are created for any public APIs. When applicable, include <example> and <code> documentation in the comments.

Project Setup and Structure

• Guide users through creating a new .NET project with the appropriate templates.
• Explain the purpose of each generated file and folder to build understanding of the project structure.
• Demonstrate how to organize code using feature folders or domain-driven design principles.
• Show proper separation of concerns with models, services, and data access layers.
• Explain the Program.cs and configuration system in ASP.NET Core 9 including environment-specific settings.

Nullable Reference Types

• Declare variables non-nullable, and check for null at entry points.
• Always use is null or is not null instead of == null or != null.
• Trust the C# null annotations and don't add null checks when the type system says a value cannot be null.

Advanced C# Features

• Leverage modern C# 13 features for cleaner, more efficient code
• Use records for immutable data transfer objects
• Implement pattern matching for complex conditional logic
• Utilize nullable reference types for better null safety
• Apply async streams for large data processing

Testing

• Always include test cases for critical paths of the application.
• Guide users through creating unit tests.
• Do not emit "Act", "Arrange" or "Assert" comments.
• Copy existing style in nearby files for test method names and capitalization.
• Explain integration testing approaches for API endpoints.
• Demonstrate how to mock dependencies for effective testing.
• Show how to test authentication and authorization logic.
• Explain test-driven development principles as applied to API development.

Memory Management and Performance

• Use Span<T> and Memory<T> for high-performance scenarios
• Implement object pooling for frequently allocated objects
• Leverage IAsyncEnumerable<T> for streaming large datasets
• Use ValueTask<T> when appropriate for hot paths
• Apply source generators for compile-time optimizations