How do you implement the strategy pattern?

Question

Accepted Answer

**Strategy** — interchangeable algorithms.

**Interface:**
```csharp
public interface IPricingStrategy
{
    decimal CalculatePrice(Order order);
}
```

**Implementations:**
```csharp
public class RegularPricing : IPricingStrategy
{
    public decimal CalculatePrice(Order order) => order.Total;
}

public class DiscountPricing : IPricingStrategy
{
    public decimal CalculatePrice(Order order) => order.Total * 0.9m;
}
```

**Usage:**
```csharp
public class OrderService(IPricingStrategy strategy)
{
    public decimal GetPrice(Order order) =>
        strategy.CalculatePrice(order);
}
```

**Key:** Strategy for algorithm flexibility.

C#: How do you implement the strategy pattern?