Visual Basic Design Patterns: VB 6.0 and VB.NET

Chapter 28. The Observer Pattern

In this chapter we discuss how you can use the Observer pattern to present data in several forms at once. In our new, more sophisticated windowing world, we often would like to display data in more than one form at the same time and have all of the displays reflect any changes in that data. For example, you might represent stock price changes both as a graph and as a table or list box. Each time the price changes, we'd expect both representations to change at once without any action on our part.

We expect this sort of behavior because there are any number of Windows applications, like Excel, where we see that behavior. Now there is nothing inherent in Windows to allow this activity, and, as you may know, programming ...