VS2010 vs VS2012 ASP.NET

I have the same project, same exact code on both VS2010 and VS2012, both targeting .NET 3.5. Running in my local machine, the following works in VS2010 but returns "" in VS2012.

requestor = User.Identity.Name;

Same web.config as well. Both running in Debug mode in IE8. What did VS2012 do to the development server? 

@pavone: Sorry to fork your question, but I think a seperate thread is required. I think the answer to your problems is in this thread.

http://channel9.msdn.com/Forums/Coffeehouse/NET-45-clarification

 Webforms. It seems to be using IIS Express, for both version I simply use the nice GUI |> Debug command but it seems they might do different things from VS2010 to VS2012... VS2010 opens a development server, VS2012 opens IIS Express, how can I get VS2012 to do the same thing as VS2010 to test my website? 

Btw I'm targeting .NET 3.5 so I don't think .NET 4.5 should affect my app, since it's not .NET 4...

[Update]

Solved it! It was definitely IIS Express giving me trouble, went into Project properties and changed it to use VS local dev server and it works as expected now. Thanks for leading me in the right direction 

2 minutes ago, pavone wrote

 Webforms. It seems to be using IIS Express, for both version I simply use the nice GUI |> Debug command but it seems they might do different things from VS2010 to VS2012... VS2010 opens a development server, VS2012 opens IIS Express, how can I get VS2012 to do the same thing as VS2010 to test my website? 

Hmmm.... what does the same code and config do on a real iis 7 server with .net 4.0 ?

two possible things i see happening:

1) Vs2012 using express is using .net 4.5 and the root asp.net web config in .net 4.5 might have different defaults for identity and such...

2) Vs 2010 using the default dev server might not be acting the way iis does

so run the same code on iis 7 or 7.5 with .net 4 and then test it with asp.net 4.5

what are the results ?