Feb 02, 2011 12:14 AM|bala.sekhar|LINK
In a given application for any data there will certain scope for its usage,
1/ within the page,
2/ Between postbacks to the same page
3/ Between multiple pages.
4/ Across user Sessions
Being said that ViewState is used for persisting the data for case 1 & 2. Where as session is used for the case 3.
And to answer your question, CanSave is something which is defined by the developer who coded it..