What is a Repository pattern in DDD context?

A Repository provides an abstraction over data access, making the domain layer independent of infrastructure concerns. It encapsulates the logic needed to access data sources.

Key principles:

• One repository per aggregate root
• Interface defined in domain layer, implementation in infrastructure
• Provides collection-like interface for accessing domain objects
• Hides database-specific details from the domain

// Domain layer interface
public interface IOrderRepository
{
    Order GetById(OrderId id);
    void Save(Order order);
    IEnumerable<Order> GetOrdersByCustomer(CustomerId customerId);
}

// Infrastructure layer implementation
public class SqlOrderRepository : IOrderRepository
{
    public Order GetById(OrderId id)
    {
        // Database-specific implementation
    }
}