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70-562 User Controls



Copying and pasting a group of control might be ok if they have minimal business logic behind, but if the control has considerable business logic behind it, it might be better to group them in a user control and copy just this one control on each page.

A user control is a like a little page that you embed within other page, they are inteded for use within a single site, so it's ok to put site specific business logic in them.

Custom controls are, like the ones in the toolbox, created from scrach and inherit from a base class, and the result is an assembly containing the control.

User controls are often used for header, footers, and side panels.

To add a user control you can drag and drop it in the page in design mode, or add in the aspx page by adding a register directive that has a src, tagname, tagprefix. And will be referenced by it's prefix:tagname and an id specific to the instance of the control.

An example,a user control can be as simple as a drop down list that provides states of a country. Since the states don't change often, they CAN be hardcoded in the control rather than comming from a db.
In this example, the events exposed by the user control have to be defined, all events of the drop down list are private to the user control. The user control will raise an event that will be handled by the page hosting the user control. This is because a user control contains usualy many controls and some might have the same events. The page then has an event handler for the selected index changed for the user control, which can be hooked up to the user control's delegate, this can be done in the Page_Load or OnInit of the page.




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