问题
I have two web applications, one running under .Net 3.5, the other has been upgraded to .Net 4.0. Prior to the upgrade, shared authentication was setup and working correctly between the two applications as indicated in the MSDN article:
http://msdn.microsoft.com/en-us/library/eb0zx8fc.aspx
The 3.5 Application is running under the Classic .NET AppPool (v2.0, Classic Pipeline).
The 4.0 application is running under the ASP .NET v4.0 AppPool (v4.0, Integrated Pipeline).
回答1:
The problem turned out to be the App Pool the .NET 3.5 application was running under. We switched the app pool to ASP .NET v4.0 Classic (without upgrading the application itself to run under 4.0 / vs2010).
Shared authentication is back to normal. I could not find this listed as a requirement anywhere so hopefully this will save someone else some time in the future.
来源：https://stackoverflow.com/questions/7826181/shared-forms-authentication-not-working-between-net-3-5-and-net-4-0-applicatio