DropDown not firing OnSelectedIndexChanged

Question

I have a page with dropdown list

   <asp:Content runat="server" ContentPlaceHolderID="ContentPlaceHolder1">
  <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
    <asp:ListItem>Cellsite</asp:ListItem>
    <asp:ListItem>Agreement</asp:ListItem>
    <asp:ListItem>Event</asp:ListItem>
    <asp:ListItem>User</asp:ListItem>
</asp:DropDownList>
<asp:Label runat="server" ID="EntityName"></asp:Label>
<ig:WebScriptManager ID="WebScriptManager1" runat="server"></ig:WebScriptManager>
<ig:WebDataGrid ID="EntityGrid" runat="server"  Width="100%">
    <Behaviors>
        <ig:Sorting>
        </ig:Sorting>
    </Behaviors>
</ig:WebDataGrid>

code behind is

     protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        EntityName.Text = DropDownList1.SelectedItem.Text;
    }

For somereason the label is never updated the event selectedindexchanged is not firing at all I need to add a dynamic grid in this event. Any clue?

Answer 1

You need to add AutoPostBack on the dropdown

 <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true">

You can actually tell that there is no post back when you do not have the AutoPostBack=true attribute.

Answer 2

set dropdownlist property AutoPostBack="true"

    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
    <asp:ListItem>Cellsite</asp:ListItem>
    <asp:ListItem>Agreement</asp:ListItem>
     <asp:ListItem>Event</asp:ListItem>
     <asp:ListItem>User</asp:ListItem>
     </asp:DropDownList>