Memory leak on the context classes

[lijunle]

Describe the bug

After a long run on my service, the memory grows a lot. After analyze the memory dump, there are lots of context classes not released.

Desktop (please complete the following information):

• OS: Windows
• .Net Target; .Net Core 2.2
• Version: v3.10.1

Additional context

This is a follow up on #306

I checked the code. It shows the BoardContext is never released. I took a quick look at the code. This line of code is strange. The Synchronized handler is never released.

https://github.com/gregsdennis/Manatee.Trello/blob/1b40470dfb1c9b6abe79b740a2a601cec37d885f/Manatee.Trello/Board.cs#L379

This seems a general issue on all context classes.

https://github.com/gregsdennis/Manatee.Trello/blob/ad33fa0a6bac4ad9fc629634ca39fdd3175bf3c7/Manatee.Trello/Card.cs#L429

[gregsdennis]

From #306 (comment)

It sounds should be a weak reference callback on the constructor.

I'll look into this idea.

[mrsalmon1976]

I'm experiencing this too. I have a Windows service running that updates board information, and after a day or so it starts suffering OutOfMemoryExceptions when calling Refresh on a board retrieved from the factory.