1:   

   2:  Module Module1

   3:   

   4:      'Define a Multicast delegate reference type that takes two integer

   5:      Public Delegate Sub CalculateTwoValuesDelegate(ByVal x As Integer, ByVal y As Integer)

   6:   

   7:      Dim WithEvents MyClassInstance2 As MyMethodClass

   8:   

   9:      Sub Main()

  10:   

  11:          Console.WriteLine("Static declaration")

  12:          MyClassInstance2 = New MyMethodClass()

  13:          MyClassInstance2.AddValues(5, 2)

  14:          MyClassInstance2.SubtractValues(5, 2)

  15:          MyClassInstance2.MultiplyValues(5, 2)

  16:   

  17:          Console.WriteLine()

  18:          Console.WriteLine("Dymanic declaration")

  19:   

  20:          'Three version of Adding Handler

  21:          '-------------------------------

  22:   

  23:          'Define an instance of the class MyMethodClass

  24:          Dim MyClassInstance As MyMethodClass = New MyMethodClass()

  25:   

  26:          '------

  27:          Console.WriteLine()

  28:          Console.WriteLine("AddHandler based on AddressOF")

  29:          AddHandler MyClassInstance.AddCalculateRequest, AddressOf MyClassInstance.Print

  30:          MyClassInstance.AddValues(6, 2)

  31:   

  32:          '------

  33:          Console.WriteLine()

  34:          Console.WriteLine("AddHandler based on Lambda expression")

  35:          AddHandler MyClassInstance.SubtractCalculateRequest, Sub(x, y) Console.WriteLine("x={0:N0},Y={1:N0}", x, y)

  36:          MyClassInstance.SubtractValues(6, 2)

  37:   

  38:          '------

  39:          Console.WriteLine()

  40:          Console.WriteLine("AddHandler based on delegate definition")

  41:          Dim MultiplyEventHandler As MyMethodClass.CalculateRequestEventDelegate = AddressOf MyClassInstance.MultiplyValues

  42:          AddHandler MyClassInstance.MultiplyCalculateRequest, AddressOf MyClassInstance.Print

  43:          MyClassInstance.MultiplyValues(6, 2)

  44:   

  45:          '------

  46:          Console.WriteLine()

  47:          Console.WriteLine("Create Instance of the delegate from my class - three separate singlecast delegate")

  48:          Dim AddInstDelegate As CalculateTwoValuesDelegate = AddressOf MyClassInstance.AddValues 'Automatically create an instance

  49:          Dim SubtractInstDelegate As CalculateTwoValuesDelegate = New CalculateTwoValuesDelegate(AddressOf MyClassInstance.SubtractValues)

  50:          Dim MultiplyInstDelegate As CalculateTwoValuesDelegate = New CalculateTwoValuesDelegate(AddressOf MyClassInstance.MultiplyValues)

  51:   

  52:          AddInstDelegate(7, 2)

  53:          SubtractInstDelegate(7, 2)

  54:          MultiplyInstDelegate(7, 2)

  55:   

  56:          '------

  57:          Console.WriteLine()

  58:          Console.WriteLine("Async Invoke AddValues by delegate in another thread")

  59:          Dim Res As IAsyncResult = AddInstDelegate.BeginInvoke(8, 2, AddressOf DelegateStartCallback, New With {.X = "AddInstDelegate"})

  60:          AddInstDelegate.EndInvoke(Res)

  61:          SubtractInstDelegate.BeginInvoke(8, 2, AddressOf DelegateStartCallback, New With {.X = "SubtractInstDelegate"})

  62:          MultiplyInstDelegate.BeginInvoke(8, 2, AddressOf DelegateStartCallback, New With {.X = "MultiplyInstDelegate"})

  63:   

  64:          '------

  65:          Console.WriteLine()

  66:          Console.WriteLine("Pass Delegates as parameter")

  67:          MySub(AddInstDelegate)

  68:          MySub(SubtractInstDelegate)

  69:          MySub(MultiplyInstDelegate)

  70:   

  71:          'VB.NET compiler will automatically instantiate a new delegate object for you, if necessary, when you use the AddressOf function.

  72:          'Three way of define delegates

  73:   

  74:          '------

  75:          Console.WriteLine()

  76:          Console.WriteLine("Full version of create instance of delegate")

  77:          Dim MulticastDelegate1 As CalculateTwoValuesDelegate = New CalculateTwoValuesDelegate(AddressOf MyClassInstance.AddValues)

  78:          'Create a new multicast Delegate using list of array of delegates

  79:          MulticastDelegate1 = CType([Delegate].Combine({New CalculateTwoValuesDelegate(AddressOf MyClassInstance.AddValues),

  80:                                                         New CalculateTwoValuesDelegate(AddressOf MyClassInstance.SubtractValues),

  81:                                                         New CalculateTwoValuesDelegate(AddressOf MyClassInstance.MultiplyValues)}

  82:                                                        ), CalculateTwoValuesDelegate)

  83:          MulticastDelegate1(10, 2)

  84:   

  85:          '

  86:          '------

  87:          Console.WriteLine()

  88:          Console.WriteLine("Alternative decraration instance of the delegate reference type (singlecast delegate)")

  89:          Dim MulticastDelegate2 As CalculateTwoValuesDelegate = AddressOf MyClassInstance.AddValues

  90:   

  91:          MulticastDelegate2 = CType([Delegate].Combine({New CalculateTwoValuesDelegate(AddressOf MyClassInstance.AddValues),

  92:                                                         New CalculateTwoValuesDelegate(AddressOf MyClassInstance.SubtractValues),

  93:                                                         New CalculateTwoValuesDelegate(AddressOf MyClassInstance.MultiplyValues)}

  94:                                                        ), CalculateTwoValuesDelegate)

  95:          MulticastDelegate2(11, 2)

  96:   

  97:          '

  98:          '------

  99:          Console.WriteLine()

 100:          Console.WriteLine("Automatily create an instance new multicast delegate using list of array of delegates")

 101:          Dim MulticastDelegate3 = CType([Delegate].Combine({New CalculateTwoValuesDelegate(AddressOf MyClassInstance.AddValues),

 102:                                                             New CalculateTwoValuesDelegate(AddressOf MyClassInstance.SubtractValues),

 103:                                                             New CalculateTwoValuesDelegate(AddressOf MyClassInstance.MultiplyValues)}

 104:                                                            ), CalculateTwoValuesDelegate)

 105:          MulticastDelegate3(12, 2)

 106:   

 107:          '

 108:          '------

 109:          Console.WriteLine()

 110:          Console.WriteLine("Dynamic invoke delegate each Delegate in InvocationList ")

 111:          Dim MulticastDelegate4 = CType([Delegate].Combine({New CalculateTwoValuesDelegate(AddressOf MyClassInstance.AddValues),

 112:                                                             New CalculateTwoValuesDelegate(AddressOf MyClassInstance.SubtractValues),

 113:                                                             New CalculateTwoValuesDelegate(AddressOf MyClassInstance.MultiplyValues)}

 114:                                                            ), CalculateTwoValuesDelegate)

 115:          Dim DelegateAsyncState = New Object

 116:          For Each OneDelegate As [Delegate] In MulticastDelegate4.GetInvocationList

 117:              OneDelegate.DynamicInvoke(13, 2)

 118:          Next

 119:   

 120:          '

 121:          '------

 122:          Console.WriteLine()

 123:          Console.WriteLine("Delegate Methods")

 124:          Dim DelegateMethods As Reflection.MethodInfo() = GetType(MyMethodClass.SubtractCalculateRequestEventHandler).GetMethods

 125:          For Each One As Reflection.MethodInfo In DelegateMethods

 126:              Console.WriteLine(One.Name)

 127:          Next

 128:          '

 129:          '

 130:          Console.WriteLine("Press any key to continue")

 131:          Console.ReadKey()

 132:      End Sub

 133:   

 134:      'pass delegate as parameters

 135:      Sub MySub(EventHandler As CalculateTwoValuesDelegate)

 136:          'invoke delegate

 137:          EventHandler.Invoke(9, 2)

 138:      End Sub

 139:   

 140:   

 141:      Sub MySub1(ByVal x As Integer, ByVal y As Integer) Handles MyClassInstance2.AddCalculateRequest, MyClassInstance2.MultiplyCalculateRequest, MyClassInstance2.SubtractCalculateRequest

 142:          Console.WriteLine("x={0:N0},Y={1:N0}", x, y)

 143:      End Sub

 144:   

 145:      Sub DelegateStartCallback(X As IAsyncResult)

 146:          Console.WriteLine(X.AsyncState.X & ", CurrentThread=" & Threading.Thread.CurrentThread.ManagedThreadId)

 147:      End Sub

 148:   

 149:   

 150:  End Module

 151:   

 152:   

 153:  'Events are essentially an accessor wrapper around a private delegate field, in the same way that properties often wrap a private field. 

 154:  'The big differences between Delegate fields And events are that events support the AddHandler And EventHandler functions 

 155:  'And events cannot be raised/invoked from outside Of the Class that defines it.

 156:   

 157:  Public Class MyMethodClass

 158:   

 159:      'Define Event without delegates (alternative decraration) - Delegate creates by compiler

 160:      Public Event AddCalculateRequest(ByVal x As Integer, ByVal y As Integer)

 161:   

 162:      'Event statement implicitly defines a delegate class named SubtractCalculateRequestEventHandler

 163:      Public Event SubtractCalculateRequest(ByVal x As Integer, ByVal y As Integer)

 164:   

 165:      'Manually Define a delegate 

 166:      Public Delegate Sub CalculateRequestEventDelegate(ByVal x As Integer, ByVal y As Integer)

 167:      'Define Event, based on delegate declaration

 168:      Public Event MultiplyCalculateRequest As CalculateRequestEventDelegate

 169:   

 170:   

 171:      Public Sub AddValues(ByVal x As Integer, ByVal y As Integer)

 172:          'First method of flash event

 173:          RaiseEvent AddCalculateRequest(x, y)

 174:          Console.Write("The sum of two values = ")

 175:          Console.WriteLine(x + y)

 176:      End Sub

 177:   

 178:      Public Sub SubtractValues(ByVal x As Integer, ByVal y As Integer)

 179:          'Second method of flash event - as method with suffix Event

 180:          SubtractCalculateRequestEvent(x, y)

 181:          Console.Write("The subtraction of two values = ")

 182:          Console.WriteLine(x - y)

 183:      End Sub

 184:   

 185:      Public Sub MultiplyValues(ByVal x As Integer, ByVal y As Integer)

 186:          RaiseEvent MultiplyCalculateRequest(x, y)

 187:          Console.Write("The multiplication of two values = ")

 188:          Console.WriteLine(x * y)

 189:      End Sub

 190:   

 191:      Public Sub Print(ByVal x As Integer, ByVal y As Integer)

 192:          Console.WriteLine("x={0:N0},Y={1:N0}", x, y)

 193:      End Sub

 194:  End Class

 195: