Delegates in Vb.NET

'delegate is poiter to particulare method of function

'events is type of delegate

Public Class Wisdom 'Class containing Delegate

Delegate Function GiveAdvice() As String

Public Function OfferAdvice(ByVal Words As GiveAdvice) As String

Return (Words())

End Function

End Class

Public Class Parent 'Base type

Public Overridable Function Message() As String

Return ("You should listen to your elders")

End Function

End Class

Public Class Dad 'derived from the base parent type

Inherits Parent

Public Overrides Function Message() As String

Return ("You should listen to your Mom")

End Function

End Class

Public Class Mom 'derived from the base parent type

Inherits Parent

Public Overrides Function Message() As String

Return ("You should listen to your Dad")

End Function

End Class

Public Class Daughter 'not derived from the base parent type

Public Function Message() As String

Return ("I know all there is to life")

End Function

End Class

Public Function CallAdvice(ByVal p As Parent) As String

Dim objParents As New Wisdom

Dim TeenAgeGirl As Wisdom.GiveAdvice = New Wisdom.GiveAdvice(AddressOf p.Message)

Return (objParents.OfferAdvice(TeenAgeGirl))

End Function

Sub Main()

Dim objDad As New Dad

Dim objMom As New Mom

Dim objDaughter As New Daughter

'console.WriteLine(CallAdvice(objDad))

'console.WriteLine(CallAdvice(objMom))

MsgBox(CallAdvice(objMom))

'will not work as this is not derived

'console.WriteLine(CallAdvice(objDaughter))

End Sub

 

OutPut : will not work as this is not derived