Take the following example (foobar could be any type of object that exposes an event I want to handle...):
sub DoThis()
dim i as integer = 0
dim o as FooBarObject
for i = 0 to 5
o = new FooBarObject(...)
AddHandler o.SomeEvent, addressof FooBarEventHappened
next
end sub
sub FooBarEventHappened()
...
end sub
End Result: I've created 6 new foobar objects that will cause FooBarEventHappened to run. I have not maintained any obvious references to the 6 foobar objects I created - there is no collection or array object containing a reference to the objects for later use. The CLR however knows not to garbage collect my foobar objects because there is an event handler for their events.
How can I now get a reference to each of the foobar objects created based on the fact that FooBarEventHappened is registered to handle the event?
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This is mostly a hypothetical question - I want access to all objects (and specifically FooBar objects) that are set to call FooBarEventHappened for one of their events. I do not want to wait for FooBarEventHappened to be called (where typically you'd use the sender object) which would only return the sending object anyway.
I'm betting that through reflection you can find it. There must be some way to find all delegates objects that point to a method in an object. The CLR knows about them....
I'm still stumped on this one - it could definately be a powerful tool however, and if nothing else, learn yet another way to fool 'round with events!
There is the System.Reflection.EventInf
EventInfo Class:
http://msdn.microsoft.com/
Bob
Using reflection to get a list of event subscribers:
http://dotnetjunkies.com/W
Bob
Just thinking out loud, Bob, the dotnetjunkies article and system.reflect.eventinfo class both assume that you're working from the object that causes the events to be raised, not from the delegate reciever.
Perhaps the approach should be I need some way to find all objects that are associated with the class instance, iterate through those objects and use relection on them to determine if there is a subscription to one of their events pointing to the delegate method in question.... (using something like the dotnetjunkies article)
How do I find all object instances assiciated with a class instance? Again, this is something that the CLR knows...
Maybe getting closer?
let me see if I have this straight ...
sub DoThis()
dim i as integer = 0
dim o as FooBarObject
for i = 0 to 5
o = new FooBarObject(...)
AddHandler o.SomeEvent, addressof FooBarEventHappened
next
end sub
sub FooBarEventHappened()
...
end sub
sub SomeOtherSub()
'you want to iterate through the objects associated to FooBarEventHappened
end sub
is this assessment correct ?
The entire premise of this question appears to be wrong (the objects that are only referenced through an event are kept).
the following code illustrates that they are in fact not kept and will be garbage collected. Attempting to recover references to these objects will at best result in undefined behavior variant upon garbage collection.
Module Module1
Public Class FooBarObject
Public Event SomeEvent(ByVal sender As FooBarObject)
Private m_Name As String
Public Property Name() As String
Get
Return m_Name
End Get
Set(ByVal Value As String)
m_Name = Value
End Set
End Property
Protected Sub OnSomeEvent()
RaiseEvent SomeEvent(Me)
End Sub
Public Sub New()
End Sub
Protected Overrides Sub Finalize()
Console.WriteLine(Me.Name + " finalize called")
End Sub
End Class
Sub DoThis()
End Sub
Sub FooBarEventHappened(ByVal sender As FooBarObject)
Console.WriteLine("Receive
End Sub
Sub Main()
Dim i As Integer = 0
Dim o As FooBarObject
Console.WriteLine("Creatin
For i = 0 To 5
o = New FooBarObject
o.Name = "Object #" + (i + 1).ToString()
AddHandler o.SomeEvent, AddressOf FooBarEventHappened
Next
Console.WriteLine("Objects
Console.WriteLine("Garbage
GC.Collect(GC.MaxGeneratio
System.Threading.Thread.Sl
Console.WriteLine("Exittin
End Sub
End Module
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by: S-TwilleyPosted on 2005-02-17 at 15:50:11ID: 13341010
Is there any reason for needing a reference to each of the objects? For instance, do you need to know which object in particular triggered the event?