asp:DropDownList用法

  <asp:DropDownList runat="server" ID="drop" AutoPostBack="true" OnSelectedIndexChanged="drop_SelectedIndexChanged"></asp:DropDownList>

        protected void Page_Load(object sender, EventArgs e)
        {
            //EF引入数据，或者自定义的list<对象>集合
            using (testEntities db =new testEntities()) {
                this.drop.DataSource = db.users.ToList();
                //显示的
                this.drop.DataTextField = "userName";
                //实际值
                this.drop.DataValueField = "id";
                this.drop.DataBind();
            }
        }

        protected void drop_SelectedIndexChanged(object sender, EventArgs e)
        {
            string selectedValue = this.drop.SelectedValue;
            int selectedIndex = this.drop.SelectedIndex;
            ListItem selectedItem = this.drop.SelectedItem;
        }