Answer Posted / kiran
Delegate is a class that can hold a reference to a method
or a function.Delegate class has
a signature and it can only reference those methods whose
signature is compliant with the
class.Delegates are type-safe functions pointers or
callbacks.
Below is a sample code which shows a example of how to
implement delegates.
Public Class FrmDelegates
Inherits System.Windows.Forms.Form
Public Delegate Sub DelegateAddString()
Private Sub FrmDelegates_Load(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
Private Sub AddString()
lstDelegates.Items.Add(“Running AddString() method”)
End Sub
Private Sub cmdDelegates_Click(ByVal sender As
System.Object,
ByVal e As System.EventArgs) Handles cmdDelegates.Click
Dim objDelegateAddString As DelegateAddString
objDelegateAddString = AddressOf AddString
objDelegateAddString.Invoke()
End Sub
End Class
In the above there is a method called “AddString()” which
adds a string to a listbox.You
can also see a delegate declared as :-
Public Delegate Sub DelegateAddString()
This delegate signature is compatible with the “AddString”
method.When i mean
compatibility that means that there return types and
passing parameter types are same.Later in command click of
the button object of the Delegate is created and the method
pointer
is received from “AddressOf ” keyword.Then by using
the “Invoke” method the method
is invoked.
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