The Sign-In related files in the \Shared and \App_Code\Shared folders are replaced by new versions from the ProjectTemplates folder.
During migration, existing Sign-In related files are replaced with new Sign-In files. These files will be replaced in your application with newer versions from the Project Templates folder.
…\Shared\SignIn_Control.ascx
…\Shared\SignIn_Control.ascx.cs (vb)
…\App_Code\Shared\SignIn_Control.Controls.cs (vb)
…\App_Code\Shared\SignInState.cs (vb)
…\App_Code\Shared\Crypto.cs (vb)
Customizations you have made to these files will not be retained. If you have customized these files, then you must re-apply your customizations to the new files.
After migration, re-apply any customizations you may have made to the original Sign-In files to the new Sign-In files in your application.
Version 6.0 Application Migration