Delegates + Remove method

[sonia.sardana]

 Public Delegate Sub BeginingDelegate()

    Public Sub SingleCall1()
        MsgBox("Delegate 1")
    End Sub

    Public Sub SingleCall2()
        MsgBox("Delegate 2")
    End Sub

    Public Sub SingleCall3()
        MsgBox("Delegate 3")
    End Sub

'USE COMBINE METHOD
 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Call1 As BeginingDelegate
        Dim Call2 As BeginingDelegate
        Dim Call3 As BeginingDelegate

        Call1 = AddressOf SingleCall1
        Call2 = New BeginingDelegate(AddressOf SingleCall2)
        Call3 = New BeginingDelegate(AddressOf SingleCall3)
        Dim multiExecution As BeginingDelegate = CType([Delegate].Combine(Call1, Call2, Call3), BeginingDelegate)
        multiExecution.Invoke()
    End Sub

'USE REMOVE METHOD
 Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim Call1 As BeginingDelegate
        Dim Call2 As BeginingDelegate

        Call1 = AddressOf SingleCall1
        Call2 = New BeginingDelegate(AddressOf SingleCall2)

        Dim multiExecution As BeginingDelegate = CType([Delegate].Remove(multiExecution, Call2), BeginingDelegate)
        multiExecution.Invoke()
    End Sub

Combine method is working successfully,But Remove method not working Successfully .Now I want to remove delegate SingleCall2 on Button2_Click,I want that only SingleCall1 and SingleCall3 are invoked. Help in correcting the code.

[stanav]

You have to reference to the same multiExecution delegate which you combined in button1.click.
To do that, you can declare the delegate variables with class scope. Try this:

Dim multiExecution As BeginingDelegate
Dim Call1 As BeginingDelegate
Dim Call2 As BeginingDelegate
Dim Call3 As BeginingDelegate

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Call1 = AddressOf SingleCall1
        Call2 = New BeginingDelegate(AddressOf SingleCall2)
        Call3 = New BeginingDelegate(AddressOf SingleCall3)
        multiExecution  = CType([Delegate].Combine(Call1, Call2, Call3), BeginingDelegate)
        multiExecution.Invoke()
    End Sub

'USE REMOVE METHOD
 Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
       
        Dim delegateRemoved As BeginingDelegate  = CType([Delegate].Remove(multiExecution, Call2), BeginingDelegate)
        delegateRemoved.Invoke()
    End Sub

[sonia.sardana]

hi stanav,I m getting the error Object reference not set to an instance of an object.

[stanav]

You have to click button1 first so that you combine call1, call2 and call3 into the multiExecution delegate. After that, you click button2 to remove one of the delegate from the list.
If you launch your app and click button2 right away, of course you will get a null exception because your multiExecution delegate is not yet initialized.

[sonia.sardana]

Sir i m just asking that only na,How to initialize it on Button2 click