garbage collection - Cost to GC of using weak references in C#? -

In it, say:

Another concern is that runtime with weak use Overheads are references The obvious cost is to create weak references and call them on. A less obvious cost is that every time a GC is run important extra work is required.

So what is the cost for the weak referee's GC? Does the extra work need to be done, and how big is this deal? I can make some educated guesses, but I am interested in real mechanics.

Please check the Jeffrey Richter article about this article.