Design Patterns

The Strategy Pattern: A Design Pattern for Flexible Algorithms

nemostorm•January 11, 2026•12 min read

The Strategy Pattern: A Design Pattern for Flexible Algorithms

What is the Strategy Pattern?

The Strategy Pattern is a behavioral design pattern that enables selecting an algorithm's behavior at runtime. Instead of implementing a single algorithm directly, code receives runtime instructions about which in a family of algorithms to use.

The Problem It Solves

Imagine you're building a payment processing system. You need to support multiple payment methods: credit card, PayPal, cryptocurrency, and bank transfer. Without the Strategy Pattern, you might end up with code like this:

csharp

public class PaymentProcessor
{
    public void ProcessPayment(decimal amount, string method)
    {
        if (method == "credit-card")
        {
            // Credit card logic
            Console.WriteLine("Processing credit card payment...");
        }
        else if (method == "paypal")
        {
            // PayPal logic
            Console.WriteLine("Processing PayPal payment...");
        }
        else if (method == "crypto")
        {
            // Cryptocurrency logic
            Console.WriteLine("Processing crypto payment...");
        }
        else if (method == "bank-transfer")
        {
            // Bank transfer logic
            Console.WriteLine("Processing bank transfer...");
        }
    }
}

Conclusion

The Strategy Pattern is a powerful tool for writing flexible, maintainable code. By encapsulating algorithms into separate classes, you create a system that's easy to extend, test, and modify. Whether you're processing payments, sorting data, or validating input, the Strategy Pattern helps you build robust applications that can adapt to changing requirements.

Remember: favor composition over inheritance, and always keep your code open for extension but closed for modification.