状态保持
private void dropdownlist1Value(object sender)
  {
  DropDownList ddl = sender as DropDownList;
  for (int i = 1; i <= Convert.ToInt32(ViewState["Pagecount"]); i++)
  {
  ListItem li = new ListItem();
  li.Text = i.ToString();
  li.Value = i.ToString();
  ddl.Items.Add(li);
  }
  }

------解决方案--------------------
http://www.cnblogs.com/wwan/archive/2010/11/18/1880357.html楼主是不是想问viewstate？怎么操作啊
http://www.cnblogs.com/aierong/archive/2008/12/04/viewstate.html
http://zhidao.baidu.com/question/55153985.html