navigation bar inside a user control?

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ASP.NET

Hello

On a web site, the code to handle an event coming from the usercontrol which contains my navigation bar on Windows server 2003 iis is writing like this :

navigationBar.Selec += new navigationBar_ascx.SelectEventHandler(onSelection);

on the index page of the site

and Inside the navigationBar.ascx is writing like this:
public delegate void SelectEventHandler( object sender, EventsArgs e)
public event SelectEventHandler Select;
.....

But on Windows server 2008 or 2012 iis the compilator don't accepts navigationBar_ascx?

Why this difference and how rectified this error?

Thank you