protected void Page_Load(object sender, EventArgs e) { if(Session["id"] == null) { //一般应跳转页面 } int id = Convert.ToInt32(Session["id"]); if (!IsPostBack) { //这里绑定DropDownList DropDownList1.Items.Add(new ListItem("aa", "1")); DropDownList1.Items.Add(new ListItem("bb", "2")); } DropDownList1.SelectedValue = id.ToString(); }