联动的DropDownList控件只能读取到第一项的值

Question

DropDownList1启用了autopostback，
DropDownList2取消了autopostback，
现在DropDownList2能根据DropDownList1的值来读取数据，
但是无论怎么选Response.Write(DropDownList2.SelectedItem.Text)  显示出来的值总是DropDownList2里面的第一项
大神们，到底是哪里出问题啦？？？

Answer 1

public partial class member_mb_apply : System.Web.UI.Page
{
    itemBLL ib = new itemBLL();
    memberBLL mb = new memberBLL();
    applyBLL ab = new applyBLL();
    protected void Page_Load(object sender, EventArgs e)
    {
        string mname = DropDownList1.SelectedValue.ToString();
        DropDownList2.DataSource = ib.getallitem(mname);
        DropDownList2.DataTextField = "item";
        DropDownList2.DataValueField = "item";
        DropDownList2.DataBind();
        string id = Session["id"].ToString();
        register r = mb.SelectRecordByid(id);
        TextBox1.Text = r.name;
        TextBox2.Text = r.id;
        TextBox3.Text = r.sex;
        TextBox4.Text = r.birthday.ToString();
    }
    protected void Button6_Click(object sender, EventArgs e)
    {
        apply a = new apply();
        a.mname = DropDownList1.SelectedItem.Text;
        a.item = DropDownList2.SelectedItem.Text;
        a.name = TextBox1.Text;
        a.id = TextBox2.Text;
        a.sex = TextBox3.Text;
        a.birthday =DateTime.Parse(TextBox4.Text);
        a.phone = TextBox5.Text;
        a.team = TextBox6.Text;
        ab.Insertapply(a);
        Response.Write("<script>alert('报名成功!');</script>");
    }
}

Answer 2

    protected void Page_Load(object sender, EventArgs e)
    {
      if(!IsPostBack)
      {
        string mname = DropDownList1.SelectedValue.ToString();
        DropDownList2.DataSource = ib.getallitem(mname);
        DropDownList2.DataTextField = "item";
        DropDownList2.DataValueField = "item";
        DropDownList2.DataBind();
        string id = Session["id"].ToString();
        register r = mb.SelectRecordByid(id);
        TextBox1.Text = r.name;
        TextBox2.Text = r.id;
        TextBox3.Text = r.sex;
        TextBox4.Text = r.birthday.ToString();
      }
    }
    

Answer 3

嗯，同样楼上的，不要每次都在pageload初始化加载控件数据，加ispostback判断

Answer 4

Refer:
http://www.cnblogs.com/insus/archive/2013/05/10/3070348.html
http://www.cnblogs.com/insus/archive/2012/10/16/2725307.html
http://www.cnblogs.com/insus/archive/2011/07/04/2097059.html