listview 中 dropdownlist提交以后selectIndex不发生变化

Question

事件提交到后台了，但是把sender转换为DropDownList后selectIndex还是原来的值。把它放在页面里就可以。

Answer 1

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {        }
    }

Answer 2

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            PageInfo pageInfo;
            if (ViewState["PageInfo"] == null)
            {
                pageInfo = new PageInfo();
                ViewState["PageInfo"] = pageInfo;
            }
            pageInfo = ViewState["PageInfo"] as PageInfo;
            SqlBookDao dao = new SqlBookDao();
            ListView1.DataSource = dao.SelectList(pageInfo);
            ListView1.DataBind();
        }
    }这个设置了
  protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList ddl = sender as DropDownList;
        string ss = ddl.SelectedValue;
        string s = "";
    }ss永远是"0"

Answer 3

 <LayoutTemplate>
<tr runat="server"><asp:DropDownList ID="Pager" runat="server" OnLoad="Pager_Load" OnSelectedIndexChanged="Pager_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList></tr> </LayoutTemplate>