You must have heard this question in the developer community or in online forums, or at least at your work place. Though, the concept of user and server controls in .NET is pretty old, some developers still get confused when it comes to making a choice between both of them. I myself used to go wrong with the selection and would pick one over the other, mainly because of a very thin line (ok ok..I heard you..a little thick) between them.
Up until now, I was fond of using UserControl for all of my projects. The ratio of picking a user control over server control always used to be somewhere close to 10:1 (probabilistically, 1.0 to 0.1) for me. However, it was then when I received a comment for my experimental work on Code Project article MultiSelect Dropdown Control about my decision being an unthoughtful over choosing a UserControl as the parent class, I decided to enlighten myself more about both the control types and find out why I feel it a thin line what is a very clear distinction, and why I fail to take their design guidelines into account when it comes to authoring them.
I believe one of the important reasons to go for a user control is its simplistic nature. It can be created as easily as a web page and Its design time development support for authoring makes things a lot easier. We don’t need to override the Render() method as we get out-of-the-box support for rendering. A user control is more suitable choice when target control is composite (a collection of other intrinsic controls) in nature and has a lot of static data. On the downside, it is less convenient for advanced scenarios due to its tight coupling with the application it is built for. If the same user control needs to be used in more than one application, it introduces redundancy and maintenance problems as its source form (.ascx) needs be copied and its reference must be provided on the hosting web page. We don’t get to see this kind of problem while dealing with server controls. A server control can be a best choice in the following scenarios:
- Dynamically generated content
- zero maintenance ― single DLL which can also be added in the GAC
- Support to add the control in Visual Studio Toolbox.
A server control helps reduce redundancy as it is only a single DLL which can very easily be consumed in more than one application. According to Microsoft Support
"A server control is more suited for when an application requires dynamic content to be displayed; can be reused across an application, for example, for a data bound table control with dynamic rows”
Server controls provide full design-time support when used in a design-time host. It can be added to the toolbox of a visual designer and dragged and dropped onto a page. However, I believe the biggest disadvantage of using a server control is that, it requires to be written from the scratch for which one has to have a good understanding of page lifecycle and the order in which events execute which is normally taken care of in user controls.
Now, coming back to the title of my post "what should we choose", a user control or a server control? I would say such a decision should be a thoughtful one. If you want rapid application development (RAD) with full design time support without understanding the page life cycle, user control is the way to go. On the other hand, If ease of deployment with no redundancy and maintenance headaches is more important for you, think about custom server control.