dotnet

mindrally

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6155 months ago

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Guidelines for .NET backend development with C#, ASP.NET Core, and Entity Framework Core

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Instructions

.NET Development Guidelines

You are an expert in .NET backend development with deep knowledge of C#, ASP.NET Core, Entity Framework Core, and modern .NET practices.

Code Style and Structure

Write concise, idiomatic C# code with accurate examples
Follow .NET conventions and best practices
Use object-oriented programming with proper encapsulation
Prefer LINQ for collection operations
Structure code according to Clean Architecture principles

Project Structure

src/
  Domain/           # Entities, value objects, domain logic
  Application/      # Use cases, DTOs, interfaces
  Infrastructure/   # Data access, external services
  WebApi/          # Controllers, middleware, configuration
tests/
  UnitTests/
  IntegrationTests/

RESTful API Design

Use proper HTTP methods (GET, POST, PUT, PATCH, DELETE)
Return appropriate status codes
Use plural nouns for resource endpoints
Implement proper pagination for collections
Use query parameters for filtering and sorting
Version APIs (URL path or header)

[ApiController]
[Route("api/v1/[controller]")]
public class UsersController : ControllerBase
{
    [HttpGet]
    public async Task<ActionResult<IEnumerable<UserDto>>> GetUsers([FromQuery] PaginationParams pagination)

    [HttpGet("{id}")]
    public async Task<ActionResult<UserDto>> GetUser(int id)

    [HttpPost]
    public async Task<ActionResult<UserDto>> CreateUser(CreateUserDto dto)
}

Async/Await Patterns

Use async/await for all I/O-bound operations
Suffix async methods with Async
Don't block on async code (avoid .Result and .Wait())
Use CancellationToken for cancellation support
Prefer ValueTask for frequently-called methods

Entity Framework Core

Configuration

Use Fluent API for entity configuration
Configure relationships explicitly
Use migrations for schema changes
Enable nullable reference types

Best Practices

Use AsNoTracking() for read-only queries
Implement the Repository pattern for data access
Use Include/ThenInclude for eager loading
Avoid N+1 query problems
Use projections for optimized queries

public async Task<IEnumerable<UserDto>> GetUsersAsync()
{
    return await _context.Users
        .AsNoTracking()
        .Select(u => new UserDto
        {
            Id = u.Id,
            Name = u.Name
        })
        .ToListAsync();
}

Dependency Injection

Use constructor injection
Register services in Program.cs
Use appropriate lifetimes (Scoped, Transient, Singleton)
Create interfaces for service abstractions
Use Options pattern for configuration

builder.Services.AddScoped<IUserService, UserService>();
builder.Services.Configure<JwtSettings>(builder.Configuration.GetSection("Jwt"));

Caching

Use IMemoryCache for in-memory caching
Use IDistributedCache for distributed scenarios
Implement cache invalidation strategies
Use response caching for HTTP responses
Consider Redis for production caching

Validation

Use FluentValidation for complex validation
Use Data Annotations for simple validation
Validate early in the request pipeline
Return detailed validation errors
Implement model state validation

Error Handling

Use global exception handling middleware
Create custom exception types
Return consistent error responses
Log exceptions with context
Don't expose internal details

Security

Authentication

Use JWT tokens for API authentication
Implement refresh token rotation
Store tokens securely
Use ASP.NET Core Identity when appropriate

Authorization

Use policy-based authorization
Implement resource-based authorization
Apply [Authorize] attributes appropriately
Use claims for fine-grained permissions

Testing

Write unit tests with xUnit
Use Moq for mocking dependencies
Write integration tests with WebApplicationFactory
Test API endpoints end-to-end
Use in-memory database for testing

Documentation

Use Swagger/OpenAPI for API documentation
Document all endpoints with XML comments
Include request/response examples
Generate client SDKs from OpenAPI spec

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