Delphi Programming Guide
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Part I - Foundations
  Chapter 1 Delphi 7 and Its IDE
  Chapter 2 The Delphi Programming Language
  Chapter 3 The Run-Time Library
  Chapter 4 Core Library classes
  Chapter 5 Visual Controls
  Chapter 6 Building the User Interface
  Chapter 7 Working with Forms
Part II - Delphi Object-Oriented Architectures
  Chapter 8 The Architecture of Delphi Applications
  Chapter 9 Writing Delphi Components
  Chapter 10 Libraries and Packages
  Chapter 11 Modeling and OOP Programming (with ModelMaker)
  Chapter 12 From COM to COM+
Part III - Delphi Database-Oriented Architectures
  Chapter 13 Delphi's Database Architecture
  Chapter 14 Client/Server with dbExpress
  Chapter 15 Working with ADO
  Chapter 16 Multitier DataSnap Applications
  Chapter 17 Writing Database Components
  Chapter 18 Reporting with Rave
Part IV - Delphi, the Internet, and a .NET Preview
  Chapter 19 Internet Programming: Sockets and Indy
  Chapter 20 Web Programming with WebBroker and WebSnap
  Chapter 21 Web Programming with IntraWeb
  Chapter 22 Using XML Technologies
  Chapter 23 Web Services and SOAP
  Chapter 24 The Microsoft .NET Architecture from the Delphi Perspective
  Chapter 25 Delphi for .NET Preview: The Language and the RTL
  Appendix A Extra Delphi Tools by the Author
  Appendix B Extra Delphi Tools from Other Sources
  Appendix C Free Companion Books on Delphi
  List of Figures    
  List of tables    
  List of Listings    
  List of Sidebars  

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Chapter 12: From COM to COM+


For about 10 years, starting soon after the release of Windows 3.0, Microsoft has been promising that its operating system and its API would be based on a real object model instead of functions. According to the speculations, Windows 95 (and later Windows 2000) should have been based on this revolutionary approach. Nothing like this happened, but Microsoft kept pushing COM (Component Object Model), built the Windows 95 shell on top of it, pushed applications integration with COM and derivative technologies (such as Automation), and reached the peak by introducing COM+ with Windows 2000.

Now, soon after the release of the complete foundation required for high-level COM programming, Microsoft has decided to switch to a new core technology, part of the .NET initiative. My impression is that COM wasn't really suited for the integration of fine-grained objects, although it succeeded in providing an architecture for integrating applications or large objects.

In this chapter, you'll build your first COM object; I'll stick to the basic elements to let you understand the role of this technology without delving heavily into the details. We'll continue by discussing Automation and the role of type libraries, and you'll see how to work with Delphi data types in Automation servers and clients.

In the final part of the chapter, we'll explore the use of embedded objects, with the OleContainer component, and the development of ActiveX controls. I'll also introduce stateless COM (MTS and COM+) technologies and a few other advanced ideas including the .NET integration support offered by Delphi 7.

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