( Design Patterns ) Behavioral D

Definition

Defines the steps of an algorithm and allows subclasses to provide the implementation for one or more steps.

Components

1. AbstractClass: Defines a group of basic methods and template methods. Template Methods define the order of executing basic methods. Basic Methods let subclasses to override or implement。
2. ConcreteClass：Inheret from Abstract Class that implements the basic methods which defined by Abstract Class.
   Template Method Pattern UML

Code

 //Abstract Class
    public abstract class AbstractClass
    {
        //basic methods
        protected abstract void SimpleMethod1();

        protected abstract void SimpleMethod2();

        //template methods
        public void templateMethod()
        {
            SimpleMethod1();
            SimpleMethod2();
        }
    }

    //Concrete methods
    public class ConcreteClass : AbstractClass
    {

        protected override void SimpleMethod1()
        {
            Console.WriteLine("method1");
        }

        protected override void SimpleMethod2()
        {
            Console.WriteLine("method2");
        }

    }

    //Client class
    public class Client
    {
        public static void Main(String[] args)
        {
            ConcreteClass class1 = new ConcreteClass();
            class1.templateMethod();
        }
    }

Advantages

1. Open Close Principle.
2. The behavior(orders of executing basic methods) is controlled by parent class, subclasses are only for implementation. Easy to extend.

Reference
Design Patterns 1 of 3 - Creational Design Patterns - CodeProject
Head First Design Patterns - O'Reilly Media