The focus of the book is on COM Interoperability (since it's a much larger subject), and the heart of the discussion is broken down into four parts: Using COM Components Within the .NET Framework; Using .NET Framework Components from COM; Designing Good .NET Framework Components for COM Clients; Designing Good COM Components for .NET Framework Clients. The scope of the book is just about everything related to using "unmanaged code" in the .NET Framework. Technologies built on top of COM Interoperability are also covered-Interoperability of Windows Forms Controls and ActiveX controls, Interoperability with COM+, and Interoperability with Distributed COM (DCOM). Although Platform Invocation Services is a separate technology from COM Interoperability, there are many areas of overlap, so including in the book is a natural fit. All of these technologies are a core part of the Common Language Runtime and .NET Framework, and will likely be used not only as the path of migration for existing software projects, but for brand new software development for the next several years.