Viewstate changes not persisting while using updatepanel

Hi,
it's urgent. Can any one suggest me.

Here is my scenario

I have public property which contains some object. I'm saving that object in viewstate. When I use update panel and doing partial postback, the changes which I made to  my public property are not persisting in viewstate.

how you are saving those in vewstate.
You could also use a session to save your object. i know it work with update panel.

//this is my property
private Dictionary<string, List<Event>> EventsDictionary
                  {
                        get
                        {
                              if (ViewState["EventsDictionary"] != null)
                              {
                                    return (Dictionary<string, List<Event>>)ViewState["EventsDictionary"];
                              }
                              else
                              {
                                    return null;
                              }
                        }
                        set
                        {
                              ViewState["EventsDictionary"] = value;
                        }
                  }

// this is my code which modifies  EventsDictionary object and keeping in viewstate

                              Dictionary<string, List<Event>> eventDictionary = EventsDictionary;
                              Dictionary<string, string[]> weekEvents = WeekEvents;
                              ScheduleManager.CopyDayEventsToAnotherDay(ref eventDictionary);// here I'm updating my EventDictionary object.
                              EventsDictionary = eventDictionary;
                              eventDictionary = null;

Advance thanks for your help

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