CODEWITHSUNDEEP
.netvb.neteventsevent-handling
Nitram
Nitram

Reputation: 6716

.NET remove inline event handler

I got a little problem with adding and removing event handlers in Visual Basic.NET. While this is in general rather easy, I need to remove a inline event handler. Question is if and how this works.

AddHandler object.ConnectionSuccessful, Sub()
                                            RemoveHandler object.ConnectionSuccessful, Me
                                        End Sub

This is the way how I tried it, it does not work. Now the question is how do I remove this inline event handler again if not this way? I found some cruel methods to remove all event handlers from a object but this is not what I want to do. I only want to remove this one single specific event handler.

I am aware that those problem disappear if I just use a normal function and the AddressOf operator. But in this case using the inline method is just more handy.

Anyone has a idea in this matter?

Upvotes: 1

Views: 699

Answers (1)

Kratz
Kratz

Reputation: 4340

If you assign your lambda to a variable, then it is possible to do this (assuming this sort-of inline structure is close to what you want). Note that you have to Type the lambda, in this case as Action in order to refer to itself from itself. 

Module Module1

Event TestEvent As Action

Sub Main()

    Dim TestLamba As Action = Sub()
                                  Console.Write("Event!")
                                  RemoveHandler TestEvent, TestLamba
                              End Sub

    AddHandler TestEvent, TestLamba

    RaiseEvent TestEvent()

    RaiseEvent TestEvent()

    Console.ReadKey()

End Sub

End Module

If you run this test console app above, you'll see that the event is fired twice, but "Event!" is only written to the console once.

Upvotes: 2

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