Command in VB.NET

   1:      ' Command Design Pattern.

   2:      ' See description in //www.vb-net.com/ProgramTheory/Command.htm

   3:      Class MainApp

   4:          ' Entry point into console application.

   5:          Public Shared Sub Main()

   6:              ' Create receiver, command, and invoker

   7:              Dim receiver As New Receiver()

   8:              Dim command As Command = New ConcreteCommand(receiver)

   9:              Dim invoker As New Invoker()

  10:              ' Set and execute command

  11:              invoker.SetCommand(command)

  12:              invoker.ExecuteCommand()

  13:              ' Wait for user

  14:              Console.ReadKey()

  15:          End Sub

  16:      End Class

  17:   

  18:      ' The 'Command' abstract class

  19:      MustInherit Class Command

  20:          Protected receiver As Receiver

  21:          ' Constructor

  22:          Public Sub New(receiver As Receiver)

  23:              Me.receiver = receiver

  24:          End Sub

  25:          Public MustOverride Sub Execute()

  26:      End Class

  27:   

  28:      ' The 'ConcreteCommand' class

  29:      Class ConcreteCommand

  30:          Inherits Command

  31:          ' Constructor

  32:          Public Sub New(receiver As Receiver)

  33:              MyBase.New(receiver)

  34:          End Sub

  35:          Public Overrides Sub Execute()

  36:              receiver.Action()

  37:          End Sub

  38:      End Class

  39:   

  40:      ' The 'Receiver' class

  41:      Class Receiver

  42:          Public Sub Action()

  43:              Console.WriteLine("Called Receiver.Action()")

  44:          End Sub

  45:      End Class

  46:   

  47:      ' The 'Invoker' class

  48:      Class Invoker

  49:          Private _command As Command

  50:          Public Sub SetCommand(command As Command)

  51:              Me._command = command

  52:          End Sub

  53:          Public Sub ExecuteCommand()

  54:              _command.Execute()

  55:          End Sub

  56:      End Class