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We're continuing the back to the basics theme for advanced VDF developers by visiting the other side of [I]External_Function[/I]. If you haven't done so already, you should [URL="http://support.dataaccess.com/forums/blog.php?b=84"]read the first part[/URL], it's a prerequisite for understanding what I'm about to talk about here. Let's start with a simple DLL written in C++, exporting only one silly function [I]SayHello()[/I], which we'll call from our VDF program. The finished ...
Let's take a closer look at [I]External_Function[/I]. But first, there are currently two generic and well established technologies you can use from VDF to interact with external components, DLL functions and COM objects. Actually, there are several other techniques available as well, the obsolete and defunct DDE technology, and the more modern SOAP technology for example, and various other IPC mechanisms. But we'll ignore those for now. DLL and COM are the two fundamental technologies ...