Sonja just told me she had another episode posted...  I have not watched it yet, but I am sure it is good.

http://msdn.microsoft.com/msdntv/episode.aspx?xml=episodes/en/20030424NETFXSK/manifest.xml

 

Platform Invoke Tips & Tricks: Memory Ownership and Levels of Indirection

Sonja Keserovic explains memory ownership assumptions under which interop marshaler works, and the differences between using managed structures vs. classes and how this choice affects the number of levels of indirection for passed parameters.