Custom controls play very important and vital roles in development. They truly boost the productivity. They make many complex tasks easier. Building custom server controls is really fascinating job for a true developer! It is the domain where people usually enter when they desperately need it. But, I think, when some standard control does not fulfill your requirements before searching some third party control, you must go for your own. In this article we explored custom controls and their types in general and specifically focused on building an extended custom control. We built ExtendedTextBox that can be a very useful member of our control toolkit. The next two parts of the article will cover composite and fully custom controls with a working example of each. You might have noticed that we did not introduce any new event in the control as it was not required as per our analysis, yet we can add new events in a custom control, our forthcoming examples might have much to do with new events.