Attaching meta-information to an object in .NET
See the question and my original answer on StackOverflowYou may be looking for .NET 4's ConditionalWeakTable<TKey, TValue>
Simon Mourier's blog (1807 answers on StackOverflow) about Microsoft technologies C#, C/C++, .NET, WinRT, WinUI3, AOT, P/Invoke, COM, Interop, DirectX, Direct2D, Windows, ...