User Controls Introduction

A UserControl is a separate, reusable part of a page. You can put a piece of a page in a UserControl, and then reuse it from a different location. The name, UserControl, might seem a bit fancy, but actually, it's just like a regular page, with an optional CodeBehind file. A notable difference is that UserControls can be included on multiple pages, while a page can't. UserControls are used much like regular server controls, and they can be added to a page declaratively, just like server controls can.

A big advantage of the UserControl is that it can be cached, using the OutputCache functionality described in a previous chapter, so instead of caching an entire page, you may cache only the UserControl, so that the rest of the page is still re-loaded on each request.

An example where a UserControl could come in handy, is a control for showing information about a certain user on a community website. In the next couple of chapters, we will create a UserControl from scratch, make it fit to our purpose, and then use it on a page.