SOLID & Design Patterns Interview Question #23

What is the Strategy Pattern?

SOLID Principles, Design Fundamentals, Repository, Factory, Strategy & Decorator Junior Beginner

Quick Interview Answer

The Strategy Pattern defines a family of interchangeable algorithms behind a common interface. A context delegates a variable piece of behavior to the selected strategy instead of containing a large conditional block.

Detailed Explanation

Strategy is useful for pricing rules, payment processing, sorting, validation, export formats, or other behavior that varies independently from the caller.

Code Example

public interface IShippingStrategy
{
    decimal Calculate(decimal weight);
}

public class ExpressShipping : IShippingStrategy
{
    public decimal Calculate(decimal weight)
        => 15m + (weight * 2m);
}