Best Practices for Structuring Large ASP.NET Projects: A Simple Guide

Clean Architecture Project Layout:

MyApp.Domain/
├── Entities/
├── ValueObjects/
├── Enums/
├── Interfaces/
├── Events/
├── Exceptions/
└── Specifications/

MyApp.Application/
├── Commands/
├── Queries/
├── Handlers/
├── Services/
├── Interfaces/
├── DTOs/
├── Mappings/
└── Validators/

MyApp.Infrastructure/
├── Data/
│   ├── Configurations/
│   ├── Migrations/
│   └── Repositories/
├── Services/
├── External/
└── Caching/

MyApp.Web.API/
├── Controllers/
├── Middleware/
├── Filters/
├── Models/
│   ├── Requests/
│   └── Responses/
├── Configuration/
└── Extensions/

Feature-Based Structure (Alternative):

MyApp.Web.API/
├── Features/
│   ├── Orders/
│   │   ├── GetOrder/
│   │   │   ├── GetOrderQuery.cs
│   │   │   ├── GetOrderHandler.cs
│   │   │   └── GetOrderValidator.cs
│   │   ├── CreateOrder/
│   │   └── OrdersController.cs
│   ├── Users/
│   └── Products/
├── Common/
│   ├── Behaviors/
│   ├── Exceptions/
│   └── Extensions/
└── Infrastructure/

Folder Organization Within Projects

MyApp.Domain/
├── Aggregates/
│   ├── Order/
│   │   ├── Order.cs
│   │   ├── OrderItem.cs
│   │   └── IOrderRepository.cs
│   └── User/
├── Common/
│   ├── BaseEntity.cs
│   ├── IAggregateRoot.cs
│   └── DomainEvent.cs
├── ValueObjects/
│   ├── Money.cs
│   ├── Address.cs
│   └── Email.cs
└── Exceptions/
    └── DomainException.cs

Infrastructure Project Structure:

MyApp.Infrastructure/
├── Data/
│   ├── Context/
│   │   └── ApplicationDbContext.cs
│   ├── Configurations/
│   │   ├── OrderConfiguration.cs
│   │   └── UserConfiguration.cs
│   ├── Repositories/
│   │   ├── OrderRepository.cs
│   │   └── BaseRepository.cs
│   └── Migrations/
├── Services/
│   ├── EmailService.cs
│   └── FileStorageService.cs
├── External/
│   ├── PaymentGateway/
│   └── NotificationService/
└── Caching/
    └── RedisCacheService.cs

API Project Structure:

MyApp.Web.API/
├── Controllers/
│   ├── V1/
│   │   ├── OrdersController.cs
│   │   └── UsersController.cs
│   └── V2/
├── Models/
│   ├── Requests/
│   │   ├── CreateOrderRequest.cs
│   │   └── UpdateOrderRequest.cs
│   ├── Responses/
│   │   └── OrderResponse.cs
│   └── Common/
│       └── PagedResponse.cs
├── Middleware/
│   ├── ExceptionHandlingMiddleware.cs
│   └── RequestLoggingMiddleware.cs
├── Filters/
│   └── ValidateModelFilter.cs
├── Configuration/
│   ├── DependencyInjection.cs
│   └── SwaggerConfiguration.cs
└── Extensions/
    └── ServiceCollectionExtensions.cs

Specialized Structures

MyApp.BackgroundServices/
├── Jobs/
│   ├── OrderProcessingJob.cs
│   └── EmailSenderJob.cs
├── Services/
├── Configuration/
└── Extensions/

For Shared Libraries:

MyApp.Shared.Kernel/
├── Extensions/
├── Utilities/
├── Constants/
├── Attributes/
└── Interfaces/

MyApp.Shared.Contracts/
├── Events/
├── Commands/
├── Queries/
└── DTOs/

Project Dependencies

Dependency Flow:

• Web.API → Application + Infrastructure
• Application → Domain only
• Infrastructure → Domain + Application (for interfaces)
• Domain → No dependencies
• Shared.Kernel → No dependencies
• Shared.Contracts → Shared.Kernel only

File Naming Conventions

Controllers: OrdersController.cs, UsersController.cs Services: IOrderService.cs, OrderService.cs Repositories: IOrderRepository.cs, OrderRepository.cs DTOs: CreateOrderDto.cs, OrderResponseDto.cs Commands/Queries: CreateOrderCommand.cs, GetOrderQuery.cs Handlers: CreateOrderCommandHandler.cs, GetOrderQueryHandler.cs

Configuration Files Organization

MyApp.Web.API/
├── appsettings.json
├── appsettings.Development.json
├── appsettings.Production.json
├── appsettings.Staging.json
└── Configuration/
    ├── DatabaseSettings.cs
    ├── JwtSettings.cs
    └── ExternalServiceSettings.cs

This structure provides clear separation of concerns, makes navigation intuitive for large teams, and scales well as your application grows. The key is consistency across all projects and establishing clear naming conventions that everyone follows.