Below are three important differences between session and viewstate.
|Data storage location
||Browser Hidden fields
||In the same page.
||Yes. If cookies disabled will use URL Query String.
In case you are new to session and view state please see the following ASP.NET training video on importance of Session and viewstate in ASP.NET: -
You can also Buy our .NET interview question book or you can also see more .NET interview question videos
You can also see the following video on IEnumerator VS IEnumerable: -