VB Shell Programming

Chapter 12. Browser Extensions

Remember when VB 5.0 came out? It was the first appearance of the Microsoft Internet Control. A great control, really, that basically represented an instance of Internet Explorer. At the time, it seemed like there were articles everywhere exclaiming, “Write a browser in FOUR lines of code!” or “Write Your Own Internet Applications Now!” Yes, it’s true, you can write a browser with just a few lines of code or create a host of other standalone Internet applications very quickly with this control. But standalone? Wouldn’t it be cooler to write an Internet application that was integrated with Explorer automatically? Yes, it would, and this is where browser helper objects come in. Browser helper objects, or BHOs, are very similar to shell extensions. They run in-process to Explorer and are loaded every time a new instance of Explorer is started. But unlike shell extensions, they can perform a wide variety of tasks. You are limited only by your imagination in what you can do with BHOs. Why? Because once loaded, the BHO has full access to IE’s event sink. This means that, as you surf the Internet, the browser helper is right there every step of the way. BHOs can log on to your favorite web-based email site automatically as soon as you navigate to the URL, or they can automatically retrieve information from your online brokerage account. They can do just about whatever you want them to do, because BHOs have complete access to every piece of HTML that passes ...