Passing managed callback class to unmanaged code

[Kenneth Porter]

I have an unmanaged library that can accept an instance of an abstract
class and call back into it. I'm writing a wrapper for this library.

How do I wrap a managed callback in a class derived from the unmanaged
class to pass to the library?

I tried creating a managed class that carries an unmanaged callback class
which calls back into the managed class, but I can't put a handle to the
unmanaged class in the unmanaged class. (I get C3265.) So how does the
unmanaged wrapper carry something to let it call up into the managed code?

[Kenneth Porter]

Re: Passing managed callback class to unmanaged code

As usual, no sooner do I frame the question than I find the answer. In this
case, it's the gcroot template class.

A HOWTO article:

http://www.codeproject.com/KB/mcpp/ijw_unmanaged.aspx