Sunday, November 19, 2006

Adding an Event to a User Control (Code Sample)

[This was originally posted at]

I had talked about how to trigger an event from a UserControl.

This ability has many benefits, such as with refactoring. For example, suppose a UserControl is hosted on many different pages, and each page requires that the control have slightly different validation that incorporates values from the host page. One way to do this is to have the UserControl call a validation method on the host page.

Here's a code snippet you can download that shows how to have a UC call a method on its parent. The idea is to add an event member to the control, and hook it up with a delegate. (I had initially seen this technique from an article on MSDN several years ago).

This specific example has four files:

  • A UserControl - RecordNav.ascx and RecordNav.ascx.cs
  • A host page - HostRecordNav.aspx and HostRecordNav.aspx.cs

The UserControl contains an event "UpdateDate" and the host page adds a method to handle the event: RecordNav1_UpdateData.

    RecordNav1.UpdateData += new AspxDemo_Events_RecorNav.UpdateDataEventHandler(RecordNav1_UpdateData);

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