Delegate
Delegate is type which holds the method(s)
reference in an object, similar to a function pointer in C and C++,
delegates are object-oriented, type safe, and secure.
Multicast Delegate
It is a Delegate which holds the reference of
more than one methods.
Multicast delegates must contain only methods that return void, else there is a
run-time exception.
How we use delegate in VB.net programming:
public delegate sub mydlg()
Then we use the delegate by simply declaring a variable of the
delegate and assigning the sub or function to run when called. First the sub to
be called:
Private Sub message()
Console.WriteLine ( "show message" )
End Sub
now it matches our declaration of MyDlg. it's a sub routine with
no parameters. And then our test code:
Dim dlg As mydel
dlg = New mydel(AddressOf message)
dlg.Invoke()
When we invoke the delegate, the message sub is run.
For example
Module Module1
Public Delegate Sub mydel()
Public Delegate Sub mydel1(ByVal
a As Integer)
Public Sub
message()
Console.WriteLine("show
message")
End Sub
Public Sub add(ByVal
a As Integer)
Dim b As Integer
b = a + a
Console.Write("
Addition is : ")
Console.WriteLine(b)
End Sub
Sub Main()
Dim dlg As mydel
dlg =
New mydel(AddressOf
message)
dlg.Invoke()
Dim dlg1 As
mydel1
dlg1 =
New mydel1(AddressOf
add)
dlg1.Invoke(10)
End Sub
End Module
OUTPUT
