>>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?
>>
>>Thanks a lot in advance.
>
>Ctrl-Z <g>
>
>Also make sure you have System.Web.dll in your project references, since that is what the error is indicating you are missing.

Similar page works just fine. I would assume none of the pages would work without the reference.