Optimized work with Listener list

[Karnah]

Listeners list has the same problems which had NestedMarkupExtension:

1. AddListener was O(N) + constant for deleting weak refernces + memory using for 'ToList()' call. Now - O(lgN).
2. RemoveListener was O(N) + constant for deleting dead weak refernces + memory using for 'ToList()' call. Now - O(lgN).
3. Invoke and EnumerateListeners has problem with memory ('ToList()' call) + deleting dead weak refernces.

So, I hope this changing will increase perfomence on all operations with listener list.

p.s. Now Invoke method all executing under lock. It seems to me and I hope this won't have some bad effects

[Karnah]

I found an interesting problem. listener.ResourceChanged can throw an exception. Usually, I met this when there were some problems in markup (for example error when we cannot change Binding after it has been initialized).
If this error happens now - listerList will not be cleared from dead listeners. I cannot just move ClearDeadReferences to finally block because then it will not delete dead references after the listener throws an exception.
There is another old problem. If one of the listeners threw an exception - for rest listeners will not call ResourceChanged. I think this is not so good too. Can I always collect all exceptions from listeners and then throw one AggregatedException?

[konne]

@Karnah please see comment

[konne]

If this error happens now - listerList will not be cleared from dead listeners. I cannot just move ClearDeadReferences to finally block, because then will not delete dead references after the listener which throws an exception.

Can we introduce some kind of a global static list there References with these Exceptions are added and then in later runs can be just deleted. This is not perfect but a little bit like the .net garbage collection.

There is another old problem. If one of the listeners threw an exception - for rest listeners will not call ResourceChanged. I think this is not so good too. Can I always collect all exceptions from listeners and then throw one AggregatedException?

I think an AggregatedException makes sense.

@Karnah TIP for you. Install Grammarly to help you fix most of the English errors in these comments even with the unpaid version.

[Karnah]

Can we introduce some kind of a global static list there References with these Exceptions are added and then in later runs can be just deleted. This is not perfect but a little bit like the .net garbage collection.

I have an idea to make ClearDeadReferences private and always call it at the beginning of AddListener, GetListeners, and RemoveListener. Dead references will live a bit longer, but external code may not worry about a moment when we should call this.

[konne]

@Karnah please check the comments

[konne]

does it make sense to call it here? because it does not search for new dead references like in GetListeners?

[Karnah]

I did it, because of a subsequence of operations.

1. Call GetListeners -> it creates list of dead references
2. Call any other method -> references are removed before main operation

But I found a better solution which is not obvious. If wrap foreach (var listener in listeners) with try/finally and call ClearDeadReferences in finally block -> reference will be always deleted after this method call, even if calling code use break;

[konne]

can you push this change, with the "finally". That sounds great to me.