>Hi everybody,
>
>I've installed VS2008 and I was just playing with my page. I then added UpdatePanel and UpdateProgress and all of the sudden somehow I got 78 or more build errors.
>
>Ok, I panicked, took the previous copy of ASPX, found a problem (bug or feature - if the region is collapsed it is not used in Search/Replace dialog), etc.
>
>Anyway, now there is one strange error pointing to the line 1 of APSX.
>
>Error 16 'System.Web.UI.Control' does not contain a definition for 'DataItem' and no extension method 'DataItem' accepting a first argument of type 'System.Web.UI.Control' could be found (are you missing a using directive or an assembly reference?) C:\Development\Visual Studio Projects\WebSites\FCAdmin\Coordinator\People\Registration.aspx 1 1 C:\...\FCAdmin\
>
>Few minutes ago I was running the page just fine...
>
>I then was just re-arranging some code in the cs file to put all related code together.
>
>What can I do with this error?

It usually means exactly what it says - you're missing using statement at the top for a namespace or don't have a reference to the assembly. Assuming you didn't change those, then the parameters on the line of code that is causing the error is incorrect (it's the wrong type, or your passing in a different variable than you think you are, etc).