autojanet/skills/understand/languages/csharp.md

C# Language Prompt Snippet

Key Concepts

• LINQ Queries: Language-integrated queries using method syntax (.Where().Select()) or query syntax
• Async/Await with Task: Asynchronous programming model returning Task<T> for non-blocking I/O
• Generics and Constraints: Type parameters with where T : class, IDisposable constraint clauses
• Properties (get/set): First-class property syntax with backing fields, auto-properties, and init-only
• Delegates and Events: Type-safe function pointers; events provide publisher-subscriber pattern
• Attributes: Metadata annotations ([HttpGet], [Authorize]) for declarative configuration
• Nullable Reference Types: Compiler-enforced null safety with ? annotations (C# 8+)
• Pattern Matching: is, switch expressions with type, property, and relational patterns
• Records and Init-Only Setters: Immutable reference types with value equality semantics (C# 9+)
• Dependency Injection (Built-in): First-class DI container in ASP.NET Core (IServiceCollection)

Import Patterns

• using System.Collections.Generic — import a namespace for unqualified type access
• using static System.Math — import static members for direct method access
• global using — file-scoped usings applied to the entire project (C# 10)
• using Alias = Namespace.Type — type alias for disambiguation

File Patterns

• *.csproj — MSBuild project file defining targets, packages, and build properties
• *.sln — Visual Studio solution file grouping multiple projects
• Program.cs — application entry point (top-level statements in .NET 6+)
• Startup.cs — service and middleware configuration (older ASP.NET Core pattern)
• appsettings.json — hierarchical application configuration

Common Frameworks

• ASP.NET Core — Cross-platform web framework for APIs, MVC, and Razor Pages
• Entity Framework — ORM with LINQ-to-SQL, migrations, and change tracking
• Blazor — Component-based UI framework using C# instead of JavaScript
• MAUI — Cross-platform native UI for mobile and desktop applications
• xUnit — Modern testing framework with theories, facts, and dependency injection

Example Language Notes

Uses LINQ method syntax .Where().Select() to compose a query pipeline over the collection. LINQ operations are lazily evaluated — the query only executes when results are enumerated, allowing efficient composition without intermediate allocations.

The built-in DI container in ASP.NET Core registers services in Program.cs and resolves them via constructor injection, following the composition root pattern.