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I have installed .NET 4.0 to a Windows Server 2008. I have run aspnet_regiis -i.

But with my new site on IIS7 I can't seem to select v4.0 as the framework. I see 2 new app pools ASP.NET 4.0 and Classic 4.0 but surely all apps don't share the same v4.0 app pool right? What am I missing?

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You may potentially also want this hotfix: See also my question… – SamStephens Sep 29 '10 at 0:24
up vote 4 down vote accepted

Is the server x64?

In this case, you should run aspnet_regiis.exe from the C:\Windows\Microsoft.NET\Framework64\v4.0.30319 folder, not from C:\Windows\Microsoft.NET\Framework\v4.0.30319.

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To use .NET 4.0 you'll need to move your app to the Application pool. Not all apps have to share the same app pool as it's simply a way to isolate apps so basically you can create app pools to your hearts desire. What you can't do is put a .NET 3.5 app into a 4.0 pool however as the pool actually loads the .NET Framework version you configure it to into memory.

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