when is HttpContext.Current.User.Identity poulated asp.net 2.0

Hi

I was wondering when the HttpContext.Current.User.Identity object is created. If you try and access this object in the AuthenticateRequest method of the global.asax file for a page without an authentication ticket the object is nothing. However by the time the same page loads and you try and access HttpContext.Current.User.Identity in the PageLoad event of an webpage the object exists.

thanks
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