如何在没有回发或更新面板的情况下获取DropdownList的SelectedValue

Question

I have a DropDownList which i am binding on page load. i dont have any buttons or anything. as soon as user selects the value in dropdown i need to show that value in label. i am not sure why this is not working. please help.

public string SelectedStore { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
  if (!Page.IsPostBack)
      {
          BindStoresList();
      }
}
 protected void BindStoresList()
 {  storeDDList.AppendDataBoundItems = true;
    storeDDList.Items.Add(new ListItem("Select store", "-1"));
    TempCollection stores = TempDataSource.LoadForCriteria("ALL", "Code ASC");
    storeDDList.DataSource = stores;
    storeDDList.DataTextField = "DisplayName";
    storeDDList.DataValueField = "Code";
   storeDDList.DataBind();
 }
  protected void storeDDList_SelectedIndexChanged(object sender, EventArgs e)
   {
     SelectedStore = storeDDList.SelectedValue.ToString();
     selectedItem.Text = SelectedStore;
   }

I dont need any kind of jquery stuff as i am going to add gridview which binds depending on the value of dropdown..

****** EDITS *******

if i set AutoPostBack=True then on page refresh my DropDownList doesn't bind at all as you can see in Page_Load Method, it will not call BindStoresList() method.

***** ANSWER *****

For people who might get stuck with this..

i was setting the EnableViewState to True for the DropDownList , so after page refreshes the SelectedValue was getting lost. after removing the EnableviewState and setting AutoPostBack to Ture working fine...

Answer 1

You can Use JavaScript . Set the OnChange attribute for your DropDownList to call a JS function and Change your label text there:

protected void Page_Load(object sender, EventArgs e)
{
  if (!Page.IsPostBack)
      {
          BindStoresList();
          storeDDList.Attributes["onChange"] = "ChangeLabelText();";
      }
}

JS function :

<script type="text/javascript">
    function ChangeLabelText() {

     var lbl = document.getElementById("<%=lbl.ClientID%>");
     var ddl = document.getElementById("<%=ddl.ClientID%>");

     lbl.innerHTML = ddl.options[ddl.selectedIndex].text;

    }
</script>

Answer 2

您必须为下拉列表设置AutoPostBack=True ，它将自动将呼叫发送到服务器端，而无需额外的按钮。

Answer 3

You may do it using Javascript, handle the OnChange event of the DropDownList and set the text of the label you want

<asp:DropDownList ID="ddl" runat="server" onchange="ddl_change(this.value)"/>

<script language="javascript" type="text/javascript">
function ddl_change(value)
{
var lbl = document.getElementById('<%= yourlabel.ClientID %>');
lbl.value = value;
}
</script>

Good luck.