What is the point of using GC.AddMemoryPressure with an unmanaged resource?

Question

I\'ve read about this issue on MSDN and on CLR via c#.

Imagine we have a 2Mb unmanaged HBITMAP allocated and a 8 bytes managed bitmap pointing to it. What\'s the poi

Answer 1

It is provided so that the GC knows the true cost of the object during collection. If the object is actually bigger than the managed size reflects, it may be a candidate for quick(er) collection.

Brad Abrams entry about it is pretty clear:

Consider a class that has a very small managed instance size but holds a pointer to a very large chunk of unmanaged memory. Even after no one is referencing the managed instance it could stay alive for a while because the GC sees only the managed instance size it does not think it is “worth it” to free the instance. So we need to “teach” the GC about the true cost of this instance so that it will accurately know when to kick of a collection to free up more memory in the process.