REST API: PRODUCT MANAGEMENT (.NET 8)

PROJECT STRUCTURE

ProductsApi.sln
├── ProductsApi.Core
│   ├── Entities/
│   │   ├── Product.cs
│   │   └── Category.cs
│   ├── Interfaces/
│   │   ├── IProductRepository.cs
│   │   └── IUnitOfWork.cs
│   └── ValueObjects/
│       └── Money.cs (price representation)
│
├── ProductsApi.Application
│   ├── Commands/
│   │   ├── CreateProductCommand.cs
│   │   ├── UpdateProductCommand.cs
│   │   └── CreateProductCommandHandler.cs (MediatR)
│   ├── Queries/
│   │   ├── GetProductByIdQuery.cs
│   │   └── GetProductByIdQueryHandler.cs
│   ├── DTOs/
│   │   ├── CreateProductDto.cs
│   │   └── ProductResponseDto.cs
│   └── Validators/
│       └── CreateProductValidator.cs (FluentValidation)
│
├── ProductsApi.Infrastructure
│   ├── Persistence/
│   │   ├── ApplicationDbContext.cs (EF Core)
│   │   ├── Repositories/
│   │   │   └── ProductRepository.cs
│   │   └── Migrations/
│   │       └── InitialCreate.cs
│   ├── Authentication/
│   │   └── JwtTokenService.cs
│   └── Logging/
│       └── SerilogConfiguration.cs
│
└── ProductsApi.Api
    ├── Program.cs (dependency injection setup)
    ├── Endpoints/
    │   └── ProductEndpoints.cs (minimal APIs)
    └── Middleware/
        └── ExceptionHandlingMiddleware.cs

===== KEY FILES =====

DATABASE SETUP (Entities)

Product.cs:
• Id (GUID primary key)
• Name (string, required, max 100)
• Description (string, nullable)
• Price (Money value object)
• CategoryId (FK to Category)
• CreatedAt (DateTime, audit)
• UpdatedAt (DateTime, audit)

Entity configuration (Fluent API in DbContext):
• Product table has unique index on Name
• Foreign key cascade delete disabled (soft delete instead)

===== COMMANDS (CQRS) =====

CreateProductCommand
→ Input: name, description, price, categoryId
→ Validation: FluentValidation (price > 0, name length)
→ Handler: Persists to EF Core, returns ProductId
→ Response: 201 Created with Location header

UpdateProductCommand
→ Input: id, name, description, price
→ Concurrency: Optimistic locking (timestamp column)
→ Handler: Updates existing product, validates new price
→ Response: 200 OK or 409 Conflict if stale

===== QUERIES =====

GetProductByIdQuery
→ Input: productId
→ Handler: Queries EF Core with AsNoTracking (read-only optimization)
→ Response: ProductResponseDto or 404

GetProductsQuery
→ Input: pageNumber, pageSize, categoryId (optional)
→ Handler: IQueryable filtering + pagination (skip/take)
→ Response: Paginated list, includes total count header

===== ENDPOINTS (Minimal APIs) =====

app.MapGet("/products/{id}", GetProductById)
app.MapPost("/products", CreateProduct)
app.MapPut("/products/{id}", UpdateProduct)
app.MapDelete("/products/{id}", DeleteProduct)

Each endpoint:
• Validates auth (JWT middleware)
• Maps request DTO to command/query
• Uses MediatR to dispatch
• Maps response DTO for serialization

===== AUTHENTICATION (JWT) =====

JwtTokenService:
• Signs token with RSA private key (4096-bit)
• Includes claims: userId, email, role
• Expiry: 15 minutes (access token)
• Refresh token: 7 days in HttpOnly cookie

Program.cs setup:
• AddAuthentication("Bearer")
• AddJwtBearer (validate signature, expiry)
• Middleware order: Auth → Authorization

===== ERROR HANDLING =====

ExceptionHandlingMiddleware catches:
• ValidationException → 400 Bad Request
• NotFoundException → 404 Not Found
• DbUpdateConcurrencyException → 409 Conflict
• Unhandled exceptions → 500 (logged, no stack trace exposed)

Response format:
{
  "error": "Product not found",
  "traceId": "0HN1GDGA2P9R0:00000001",
  "statusCode": 404
}

===== DEPLOYMENT (AOT COMPILATION) =====

Program.cs AOT settings:
• UseNativeAot() enabled
• Reflection-free DI setup (types registered explicitly)
• Build time: dotnet publish -c Release -r linux-x64

Container image: 150 MB (vs 600+ with JIT)
Cold start: <50ms (vs 500ms with JIT)

===== MIGRATIONS =====

Initial setup:
→ Command: dotnet ef migrations add InitialCreate
→ Command: dotnet ef database update

Schema design:
• Products table (id, name, description, price, categoryId, createdAt, updatedAt)
• Categories table (id, name)
• Foreign key: Products.categoryId → Categories.id (no cascade delete)

===== TESTING =====

Test project uses:
• xUnit (test runner)
• Moq (mocking repositories)
• In-memory EF Core for integration tests

Example: CreateProductCommandHandler should create product
→ Arrange: CreateProductCommand with name, price
→ Act: Send via MediatR
→ Assert: Product persisted, ID returned, CreatedAt set