Feb 03, 2011 10:25 PM|Vince Xu - MSFT|LINK
CanSave is the variable on the server cache. After you use session("cansave"), system will create the variable for session which is saved on server. That is something like a global variable which is shared for specific user.
After you used ViewState("cansave"), asp.net will encode the "cansave" and value of it, then it will save them all to the hiddencontrol on the page after page rendering. You can check the sourcecode of the page, you will find two hidden controls which saves