What do I need Protected WithEvents for?

I've noticed "Protected WithEvents" in the declarations for my controls on an ASPX web form. What's this all about? What does it mean?
When working with web forms, you need to have Protected WithEvents preceding the controls. Well almost. Here's what each one means and does.

Protected: You have to have this. This is what establishes the link between the instance of the control that is declared in the HTML and the instance in the code-behind.

HTML Markup (mypage.aspx): 
<asp:button id="cmdClickMe" runat="server" />
Code-behind (mypage.aspx.vb): 
Protected WithEvents cmdClickMe As System.Web.UI.WebControls.Button

WithEvents: This is not always required. This is used to provide the linkup of the event handlers so that you can create a method and use Handles cmdClickMe.Click to wire in the event. If you have a control on a web form that does not require events (which is more likely than not for things like labels or text boxes) you can remove the WithEvents keyword. Usually, the things that need event wiring are buttons, radio buttons, checkboxes, selects (dropdownlist or listbox), etc. If you want to use a text box's OnChanged event, then you would need it.

Optimization

If you have a lot of controls on a page, it would probably be a little faster if you don't have WithEvents on controls that don't need it. On a page by page basis, you probably wouldn't notice it but once the application is being used my many users at the same time, things will be faster.

Where to Next?

Wonder where to go next? You can post a comment on this article.

Doc ID 300
Full URL https://imar.spaanjaars.com/300/what-do-i-need-protected-withevents-for
Short cut https://imar.spaanjaars.com/300/
Written by Imar Spaanjaars
Date Posted 05/23/2004 15:18
Date Last Updated 05/23/2004 15:25
Date Last Reviewed 06/10/2006 15:41

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