Template Method -- Design Patterns

   Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure. 

Participants

    The classes and/or objects participating in this pattern are:

• Abstract Class (Data Object)

    Defines abstract primitive operations that concrete sub classes define to implement steps of an algorithm

     Implements a template method defining the skeleton of an algorithm.

    

     The template method calls primitive operations as well as operations defined in Abstract Class or those of other objects.

• Concrete Class(Customer Data Object)

      Implements the primitive operations ot carry out subclass-specific steps of the algorithm

Example for Template Method Design Pattern

using System;  namespace Template.Structural {   /// <summary>   /// MainApp startup class for Real-World   /// Template Design Pattern.   /// </summary>   class MainApp   {     /// <summary>     /// Entry point into console application.     /// </summary>     static void Main()     {       AbstractClass aA = new ConcreteClassA();       aA.TemplateMethod();        AbstractClass aB = new ConcreteClassB();       aB.TemplateMethod();        // Wait for user       Console.ReadKey();     }   }    /// <summary>   /// The 'AbstractClass' abstract class   /// </summary>   abstract class AbstractClass   {     public abstract void PrimitiveOperation1();     public abstract void PrimitiveOperation2();      // The "Template method"     public void TemplateMethod()     {       PrimitiveOperation1();       PrimitiveOperation2();       Console.WriteLine("");     }   }    /// <summary>   /// A 'ConcreteClass' class   /// </summary>   class ConcreteClassA : AbstractClass   {     public override void PrimitiveOperation1()     {       Console.WriteLine("ConcreteClassA.PrimitiveOperation1()");     }     public override void PrimitiveOperation2()     {       Console.WriteLine("ConcreteClassA.PrimitiveOperation2()");     }   }    /// <summary>   /// A 'ConcreteClass' class   /// </summary>   class ConcreteClassB : AbstractClass   {     public override void PrimitiveOperation1()     {       Console.WriteLine("ConcreteClassB.PrimitiveOperation1()");     }     public override void PrimitiveOperation2()     {       Console.WriteLine("ConcreteClassB.PrimitiveOperation2()");     }   } }

Output ConcreteClassA.PrimitiveOperation1() ConcreteClassA.PrimitiveOperation2()