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What is Currency Exchange API?

The Currency Exchange API is a production-ready REST API built with .NET 8 that provides real-time currency conversion and exchange rate management. It automatically synchronizes exchange rates from the Central Bank of Russia (CBR) and supports intelligent rate calculations through direct, reverse, and cross-rate conversions.

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Key Features

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Automatic Rate Updates

The API includes a background hosted service (CBRExchangeRate) that periodically fetches and updates exchange rates from the Central Bank of Russia’s SOAP service. The update interval is configurable via appsettings.json.

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Intelligent Rate Calculation

When converting between currency pairs, the API intelligently:
  • Uses direct rates when available
  • Calculates and saves reverse rates automatically (e.g., if USD→RUB exists, it can calculate RUB→USD)
  • Computes cross-rates through intermediate currencies when direct pairs don’t exist

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Clean Architecture

The project follows clean architecture principles with clear separation of concerns:
  • API Layer - Controllers and HTTP concerns
  • Application Layer - Business logic and services
  • Core Layer - Domain models and interfaces
  • Data Layer - Database access and external services

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Enterprise Features

  • PostgreSQL database with Entity Framework Core
  • Input validation and error handling middleware
  • Swagger/OpenAPI documentation
  • CORS configuration
  • Docker support for easy deployment

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Technology Stack

.NET 8

Latest LTS version of .NET for high-performance APIs

PostgreSQL

Reliable relational database with EF Core ORM

Entity Framework Core

Modern ORM with LINQ support and migrations

Swagger/OpenAPI

Interactive API documentation and testing

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Additional Technologies

  • WCF SOAP Client - Integration with Central Bank of Russia service
  • Docker & Docker Compose - Containerized deployment
  • Nginx - Reverse proxy configuration (optional)

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Use Cases

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Financial Applications

  • Currency conversion for e-commerce platforms
  • Multi-currency pricing systems
  • Financial reporting with automatic rate updates

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Travel & Tourism

  • Real-time currency conversion for booking systems
  • Travel expense calculators
  • Multi-currency payment processing

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Data Analytics

  • Historical exchange rate analysis
  • Currency trend monitoring
  • Financial market data aggregation

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Core Capabilities

1

Currency Management

Create, retrieve, and search currencies with validation for codes, names, and symbols.See CurrencyController in CurrencyExchange/Controllers/CurrencyController.cs:10
2

Exchange Rate Management

Manage exchange rates between currency pairs with automatic validation and duplicate prevention.Implemented in ExchangeRateController at CurrencyExchange/Controllers/ExchangeRateController.cs:10
3

Currency Conversion

Convert amounts between any currency pair with automatic cross-rate calculation.Available via ExchangeController in CurrencyExchange/Controllers/ExchangeController.cs:10
4

Automatic Rate Updates

Background service updates rates from CBR on a configurable schedule.Implemented in CBRExchangeRate at CurrencyExchange.Data/ExternalServices/Clients/CBRExchangeRate.cs:13
The API includes comprehensive input validation using regular expressions and range checks. All currency codes are automatically converted to uppercase, and rates must be between 0 and 99,999,999.

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Project Structure

CurrencyExchange/
├── CurrencyExchange/              # API Layer
│   ├── Controllers/               # REST API endpoints
│   ├── Contracts/                 # DTOs and request/response models
│   └── Extensions/                # Middleware (exception handling)
├── CurrencyExchange.Application/  # Application Layer
│   └── Application/               # Business logic services
├── CurrencyExchange.Core/         # Core Layer
│   ├── Abstractions/              # Interfaces
│   └── Models/                    # Domain models
└── CurrencyExchange.Data/         # Data Layer
    ├── Configurations/            # EF Core configurations
    ├── Entities/                  # Database entities
    ├── ExternalServices/          # External API clients
    └── Repositories/              # Data access implementations

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Next Steps

Quick Start

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Architecture

Learn about the clean architecture design and components

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