USING WINDOWS COMPONENT SERVICES COM WITH VISUAL FOXPRO

ID# : 3576
Under Category : Tutorial Programming FoxPro
Source: www.craigberntson.com

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This session gives an overview of COM+ services, beginning with the basics of COM and how component design changes under COM+.

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This session gives an overview of COM+ services, beginning with the basics of COM and how component design changes under COM+. It then moves into creating COM+ components and how to administer COM+ applications and security. It then moves onto transaction management and transacting VFP tables using Compensating Resource Managers. Asynchronous events such as Queued Components and Loosely Coupled Events are covered. For many years, COM has been the method used to integrate and automate applications under Windows. For example, if you automate Word, Excel, or Outlook from your Visual FoxPro application, you do it through COM. COM is an acronym for the Component Object Model. It is a specification for writing reusable software that runs in component-based systems. It turns out there are two types of COM components, in-process and out-of-process. An in-process component is compiled as a DLL and requires an EXE to host it. When you call the component, it is hosted by your application EXE, thus it runs in your application s memory space on the same computer. An out-of-process component is compiled as an EXE and runs in its own memory space. There are pros and cons of each method. If the in-process DLL should crash, it could corrupt the memory space of your EXE and cause it to crash too. This isn t the case with a COM EXE. Because it runs in its own memory space, it is considered safer to run. However, the data transfer across the process boundaries from your EXE to the COM EXE takes longer than from your EXE to the COM DLL, making the EXE slower.

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