Why does registering to event with empty lambda function cause strong reference in memory?

Question

There is some sample code:

public class Publisher
    event Published()
end class

public class Subscriber
    public sub new(Publisher as Publisher)
        addhandler Publisher.Published,
            sub()

            end sub
    end sub
end class

1. Does registering to the Publisher event in Subscriber constructor prevent Subscriber from being garbage collected even if an empty lambda function, that doesn't capture Subscriber, is passed as event handler?

2. Is it the same in C#?

Edit

A simple console application to test it:

Sub Main()

    Dim Publisher As New Publisher

    For i = 1 To 1000000
        Dim Subscriber As New Subscriber(Publisher)
    Next

    GC.Collect()
    Dim TotalMemory = GC.GetTotalMemory(True)

    Trace.WriteLine(TotalMemory)
End Sub

Unfortunately, the application consumes 36 megabytes of memory after garbage collection, which means that all Subscribers stay in memory!

Debug and Release on different target frameworks 2.0, 3.0, 3.5, 4.0, 4.5 give the same results.

3. Can anyone reproduce the issue or explain why adding an event handler works with way?

Answer 1

If you don't reference anything related to Subscriber in your anonymous function, it will be compiled as static method of Subscriber class and as such it won't prevent any instances of Subscriber class to be garbage collected. You may want to look at this link - http://blogs.msdn.com/b/oldnewthing/archive/2006/08/02/686456.aspx - for more info.

UPDATED. Code below shows almost the same values of total memory, when running in Release mode (in Debug mode it indeed works as you said):

internal class Program {
    private static void Main(string[] args) {
        Console.WriteLine("Before: {0}", GC.GetTotalMemory(true));
        var pub = new Publisher();
        for (int i = 0; i < 1000000; i++) {
            var sub = new Subscriber(pub);
        }
        GC.Collect();
        Console.WriteLine("After: {0}", GC.GetTotalMemory(true));
        Console.ReadKey();
    }
}

public class Publisher {
    public EventHandler Published;
}

public class Subscriber {
    public Subscriber(Publisher pub) {
        pub.Published += delegate { };
    }        
}