using System;

  // Facade Pattern                       Judith Bishop Dec 2006

  // Sets up a library of three systems, accessed through a

  // Facade of two operations

  // Compile with csc /t:library /out:FacadeLib.dll Facade2.cs

  namespace FacadeLib {

    

  internal class SubsystemA {

    internal string A1() {

      return "Subsystem A, Method A1\n";

    }

      

    internal string A2() {

        return "Subsystem A, Method A2\n";

      }

  }

  internal class SubsystemB{

    internal string B1() {

      return "Subsystem B, Method B1\n";

    }

  }

 

  internal class SubsystemC{

    internal string C1() {

      return "Subsystem C, Method C1\n";

    }

  }

 

  public static class Facade {

    static SubsystemA a = new SubsystemA();

    static SubsystemB b = new SubsystemB();

    static SubsystemC c = new SubsystemC();

    public static void Operation1() {

      Console.WriteLine("Operation 1\n" +

      a.A1() +

      a.A2() +

      b.B1());

    }

    public static void Operation2() {

      Console.WriteLine("Operation 2\n" +

      b.B1() +

      c.C1());

    }

  }

}

/* Output:

Operation 1

Subsystem A, Method A1

Subsystem A, Method A2

Subsystem B, Method B1

Operation 2

Subsystem B, Method B1

Subsystem C, Method C1

*/

/*

SubsystemC x = new SubsystemC();

x.C1();

Facade2Main.cs(12,3): error CS0122: 'FacadeLib.SubsystemC' is inaccessible due to its protection level

Facade2Main.cs(12,22): error CS0122: 'FacadeLib.SubsystemC' is inaccessible due to its protection level

Facade2Main.cs(12,18): error CS0143: The type 'FacadeLib.SubsystemC' has no constructors defined

Facade2Main.cs(13,5): error CS0117: 'FacadeLib.SubsystemC' does not contain a definition for 'C1'

*/