public Action<int> CountChangedDelegate { get; set; }

Public Property CountChangedDelegate As Action(Of Integer)
	Get
	Set

public:
property Action<int>^ CountChangedDelegate {
	Action<int>^ get ();
	void set (Action<int>^ value);
}

member CountChangedDelegate : Action<int> with get, set

Property Value

If you set this property to null just before the list calls it then the list may still go through with the call. Your delegate can be called while this property is null.

The intention here is to provide a way for owners of the list to quickly update a counter somewhere when the list count changes. It is not intended for anything more than that. If you modify the list from within the delegate then you will not get recursive calls to the delegate.

Reference