Decorator pattern-C #3.0 Design Patterns

Decorator pattern belongs to Structural Patterns

Introduction:

The role of decorator pattern is to dynamically add new roles or States to an object. The decorated object is not "decorated.A key implementation point in the decorator pattern is that decorators both inherit the original class and contain an instantiation of it.

Implementation:

UML class diagram

     Public   Interface Icomponent { String Operation ();} /// <Summary>      /// Decorator      /// </Summary>      Public   Class Component: icomponent { # Region Icomponent members Public   String Operation (){ Return   "I'm a photo ;" ;} # Endregion } /// <Summary>      /// Modifier      /// </Summary>      Public   Class Decoratora: icomponent {icomponent component; Public Decoratora (icomponent component ){ This . Component = component ;} # Region Icomponent members Public   String Operation (){ Return Component. Operation () + "And decorated by decoratora" ;} # Endregion } /// <Summary>      /// Modifier B      /// </Summary>      Public   Class Decoratorb: icomponent {icomponent component; Public   String Addedstate = "And added state" ;Public Decoratorb (icomponent component ){ This . Component = component ;} # Region Icomponent members Public   String Operation (){ Return Component. Operation () + "And decorated by decoratorb" ;} Public   String Addedbehavior (){ Return   "And added behavior by decoratorb" ;} # Endregion } Public   Class Client { Public   Static   Void Display ( String S, icomponent component) {console. writeline (S + component. Operation () ;}} [testfixture] Public   Class Decoratortest {[test] Public   Void T1 () {var Component = New Component (); client. Display ( String . Empty, component); var decoratorb =New Decoratorb (component); client. Display ( "Hello! " , Decoratorb );}}