Template Method Design Pattern

• There is an [[algorithm]] but small parts of the algorithm may vary.
• It defines the skeleton of an algorithm in an operation, deferring some steps to [[subclass]]es.
• Template method lets [[subclass]]es redefine certains steps of an algorithm without changing the algorithm's structure.

namespace SOLID.OCP
{
    public abstract class PaymentProcessor
    {
        public void ProcessTransaction()
        {
            WithdrawMoney();
            CalculateBonus();
            SendGreetings();
        }
        protected abstract void WithdrawMoney();
        protected abstract void CalculateBonus();
        protected abstract void SendGreetings();
    }

    public class OnlineProcessor : PaymentProcessor
    {
        protected override void WithdrawMoney() {}
        protected override void CalculateBonus() {}
        protected override void SendGreetings() {}
    }

    public class PosTerminalProcessor : PaymentProcessor
    {
        protected override void WithdrawMoney() {}
        protected override void CalculateBonus() {}
        protected override void SendGreetings() {}
    }
}