Programming Excel with VBA and .NET

Use COM Applications

When Microsoft first developed COM, the company envisioned Office applications as building blocks that programmers could use to assemble customer-specific solutions. That vision has partly come true—it’s not uncommon for a Word document to include data from Excel or for a PowerPoint presentation to use Word and Excel data—however, that reality is not nearly as grand as Microsoft’s early marketing demos.

Meanwhile, Excel’s feature set has grown to include its own spellchecker, drawing tools, mail, and Internet capabilities. In many ways, there is less reason to program across applications than there once was.

But here’s the kicker: most of those new features were made possible because Microsoft implemented them as COM objects. That’s the reason Excel’s drawing tools look suspiciously like Visio objects. In fact, Microsoft’s vision came true; it’s just that Microsoft became the solution provider in the Office realm.

Is COM Modular?

While I was at Microsoft working on OLE 2.0 (later called COM), I complained to Brian Johnson about all the DLLs you had to install and register to get automation to work. “It’s not modular,” I whined. Brian looked at me and replied “It is modular; you just need all the modules!”