asp.net - Cannot store List objects into viewstate -

i trying store temporary list data can let user edit them before save database.

public list<scheduleentry> newscheduleentry {         {         string persistentname = "list_scheduleentry";         if (viewstate[persistentname] == null || !(viewstate[persistentname] list<scheduleentry>))         {             viewstate[persistentname] = new list<scheduleentry>();         }         return viewstate[persistentname] list<scheduleentry>;     } }  public list<scheduleentry> listview_coursescheduleentry_getdata() {     return newscheduleentry; } 

this not first time use technic not working. there no exception , can see listview_coursescheduleentry_getdata run until return statement.

but if change viewstate session (no other change), works fine. unfortunately should not use session here, since page transaction.

is possible viewstate's base64 encoding string broken list data?

in contrast values stored in session memory, classes stored in viewstate need marked serializable viewstate serialized page in case (as long session memory held on server, objects stored in memory without serialization). explains why works when objects stored in session , doesn't work when stored in viewstate.

therefore, adding serializable attribute scheduleentry class , related classes should solve issue:

[serializable] public class scheduleentry {     // ... } 

for details on asp.net viewstate see link.