Banking API — .NET 10 Minimal API

A production-ready Minimal REST API built with .NET 10 themed around a banking system: bank accounts, card management, and fund transfers.

Features

• Accounts – Create, read, update, and close bank accounts; query balance; list linked transfers and cards
• Cards – Issue debit/credit cards, activate, block, and cancel them
• Transfers – Initiate transfers between accounts with real-time balance updates

Architecture & Best Practices

Area	Approach
Framework	.NET 10 Minimal API
Endpoint organization	IEndpointRouteBuilder extension methods per feature
Typed results	TypedResults / Results<T1, T2, …> for full OpenAPI inference
Error handling	IExceptionHandler + RFC 9457 Problem Details
Validation	FluentValidation with inline endpoint validation
OpenAPI	AddOpenApi() / MapOpenApi() (native .NET 10)
Health checks	/health endpoint
Repository pattern	In-memory, thread-safe (ConcurrentDictionary)
CORS	Configured for development

Project Structure

BankingApi/
├── Domain/
│   ├── Models/        # Account, Card, Transfer
│   └── Enums/         # AccountStatus, CardStatus, CardType, TransferStatus
├── DTOs/              # Request/Response records
├── Repositories/      # IAccountRepository, ICardRepository, ITransferRepository
├── Services/          # Business logic (AccountService, CardService, TransferService)
├── Endpoints/         # AccountEndpoints, CardEndpoints, TransferEndpoints
├── Validation/        # FluentValidation validators
└── Infrastructure/    # In-memory repositories, exception handler, domain exceptions

BankingApi.Tests/
├── AccountsIntegrationTests.cs
├── CardsIntegrationTests.cs
└── TransfersIntegrationTests.cs

API Endpoints

Accounts

Method	Path	Description
GET	/api/accounts	List all accounts
POST	/api/accounts	Create a new account
GET	/api/accounts/{id}	Get account by ID
PUT	/api/accounts/{id}	Update account
DELETE	/api/accounts/{id}	Close account
GET	/api/accounts/{id}/balance	Get account balance
GET	/api/accounts/{id}/transfers	List transfers for account
GET	/api/accounts/{id}/cards	List cards for account

Cards

Method	Path	Description
GET	/api/cards	List all cards
POST	/api/cards	Issue a new card
GET	/api/cards/{id}	Get card by ID
PUT	/api/cards/{id}/activate	Activate a card
PUT	/api/cards/{id}/block	Block a card
DELETE	/api/cards/{id}	Cancel a card

Transfers

Method	Path	Description
GET	/api/transfers	List all transfers
POST	/api/transfers	Initiate a transfer
GET	/api/transfers/{id}	Get transfer by ID

Health

Method	Path	Description
GET	/health	Health check

Getting Started

cd BankingApi
dotnet run

OpenAPI document available at: http://localhost:5000/openapi/v1.json

Running Tests

dotnet test

All 24 integration tests cover accounts, cards, and transfers including happy paths and business rule violations.