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Visual Basic DLLs can create and support COM objects, but they cannot export functions unless you use a third-party tool (such as Desaware's SpyWorks) to add that capability to Visual Basic. |
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This book is not about creating COM objects or about how you can call methods or properties of a COM object. (My book Dan Appleman's Developing COM/ActiveX Components with Visual Basic 6.0 deals with that subject in depth.) But DLLs that implement COM objects do have support from the operating system to handle many of the features of OLE. That support takes the form of a large number of functions that are exported from the OLE system DLLs themselvesthe OLE API. Some of these functions can be useful even when called directly by an application. This book has generally avoided focusing on any one Windows subsystem, mostly because the techniques used in one are applicable to all. However, the OLE API deserves some special attention. It is the only API that makes extensive use of objects and a data structure called a GUID (Globally Unique Identifier). Learning to deal with objects and GUIDs in API functions poses a number of interesting challenges. |
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And interesting challenges are, after all, what this book is about. |
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