An overview of ASP.NET User Controls
You could have used a lot of controls in your ASP.Net pages, but sometimes you would have felt that a functionality you need is not given by these controls. Under such circumstances you can create your own user control so that you can use it in whatever way you wish.
You can create a user control by combining the html elements and the already existing controls to form a user control that has a different functionality. A user control could be a very simple one or a very complex one. It all depends on the functionalities that you incorporate in it.
The file that is used in creating a user control should have the extension .ascx. After creating such control you have to register it in the .aspx page in which you are going to use that control. The directive used for registering the user control has the following syntax,
Register TagPrefix="some_prefix" TagName="some_name_for_the_ctrl"
<TagPrefix:TagName runat="server" />
You can use the user controls to display functional block of your application in a web page. Even whole page can be converted to a user control if needed!