You can put pretty much anything, as long as it's Serializable, in the
page's ViewState and then retrieve it after a postback:
ViewState["Thing"] = myThing;
// later after postback...
myThing = (Thing)ViewState["Thing"];
There's some overhead associated with this because the ViewState is
downloaded as part of the page's html and uploaded again as part of the
request. If it's a large object you're better off saving it in the Session.
-Jason