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I am having issues with installing ASP.NET 4.0 on other servers. Everytime I install it, it seems that IIS has different app pools setup for 4.0. They are never the same. Sometimes I get ASP.NET 4.0 + ASP.NET 4.0 Classic + ASP.NET 4.0 DefaultAppPool. Other times I get more than that. Sometimes they are all set to classic. Other times just one is set to integrated. What the hell is going on here?! What controls this setup? This is making installation of my new Silverlight app frustrating for our customers because the instructions are inconsistent.

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I think I understand what you are asking. The installation of .NET 4.0 does not create or edit any application pools that I am aware of. Are you manually creating the app pool for your application? The only app pool that matters is the one that your application is using. The different app pools you are seeing were likely created for other applications and likely won't have any bearing on your application. So you could use the default app pool, but likely the path of least resistance is to create a new app pool for your application since it will likely confuse the end-user to sift through previously created application pools that were probably intended for somebody elses application.

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There are zero 4.0 app pools in IIS prior to installing .NET 4.0, so obviously they are being created sometime during that process. And this is important because during the installation of some silverlight and other web applications, they are presented with a drop-down list of AppPools to choose from. The instructions we give them do not always match what shows on the screen (we are getting calls saying "The app pool mentioned in the instructions is not on the screen") and this is becoming a problem. – Josh Stodola Dec 2 '10 at 18:13
According to:…, the .NET 4.0 install does not create new pools, it just automatically changes them over to .NET 4.0 in at least some circumstances. This blog post was the beta framework, but it sounds like it may still be applicable. – Somantra Dec 2 '10 at 19:23

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