selected index is not changing in the dropdownlist

[Avani Nimavat]

I have used one dropdown and three panels. Three panels are inside the updatepanel and the dropdown list is outside the updatepanel. I have initially hide the panels. I want to make one of the panels visible as per the selected item in the dropdownlist. The problem is when I change selection in the dropdownlist, the seletcedIndexChanged event fires, but the selected index remains -1 every time. I have set Autopostback = true in .aspx file.
Following is the code.

    <asp:DropDownList ID="ddlReportType" AutoPostBack="true" runat="server" OnSelectedIndexChanged="ddlReportType_SelectedIndexChanged" >
        <asp:ListItem Selected="True">-- Select which data you want to enter --</asp:ListItem>
        <asp:ListItem Value="Salse" Text="Salse">Salse Reports</asp:ListItem>
        <asp:ListItem Value="Inventory" Text="Inventory">Inventory Reports</asp:ListItem>
        <asp:ListItem Value="Finance" Text="Finance">Financial Reports</asp:ListItem>
    </asp:DropDownList>
    <br />
    <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
    <br />
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>

             <asp:Panel ID="pnlProductSale"  runat="server">

                 <asp:Label ID="lblCaptionSales" runat="server" Text="Total Product based sale"></asp:Label>
                 <table>
                     <tr>
                         <td>
                             Select Product
                         </td>
                         <td>
                              <asp:DropDownList ID="ddlProduct" runat="server"></asp:DropDownList>
                         </td>
                     </tr>
                     </table>


             </asp:Panel>

               <asp:Panel ID="pnlInventory" runat="server">

                 <asp:Label ID="lblInventory" runat="server" Text="Inventory"></asp:Label>
                 <table>
                     <tr>
                         <td>
                             Select Product
                         </td>
                         <td>
                              <asp:DropDownList ID="ddlProductPnl2" runat="server"></asp:DropDownList>
                         </td>
                     </tr>
                 </table>
             </asp:Panel>

            <asp:Panel ID="pnlCashFlow" runat="server">
            <asp:Label ID="lblCaption" runat="server" Text="Cashflow"></asp:Label>
    <table>
        <tr>
            <td>
                Deposit at start up
            </td>
            <td>
                Cash on hand :   <asp:TextBox ID="txtStartAmt" Text="0" AutoPostBack="true" runat="server" ></asp:TextBox>
                Credit :  <asp:TextBox ID="txtStartCredit" Text="0" AutoPostBack="true" runat="server" ></asp:TextBox>
                Debit :  <asp:TextBox ID="txtstartDebit" Text="0" AutoPostBack="true" runat="server" ></asp:TextBox>
            </td>
        </tr>

    </table>

                </asp:Panel>


            </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddlReportType" />

        </Triggers>
        </asp:UpdatePanel>

Following is the code in .cs file

   protected void Page_Load(object sender, EventArgs e)
        {
            if (Page.IsPostBack == false)
            {
                pnlCashFlow.Visible = false;
                pnlProductSale.Visible = false;
                pnlInventory.Visible = false;
            }
        }

        protected void ddlReportType_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (ddlProduct.SelectedIndex == 0)
            {
                Label1.Text = ddlProduct.SelectedValue;
                pnlCashFlow.Visible = false;
                pnlProductSale.Visible = false;
                pnlInventory.Visible = true;
            }
            else if (ddlProduct.SelectedIndex ==1)
            {
                Label1.Text = ddlProduct.SelectedValue;
                pnlCashFlow.Visible = false;
                pnlProductSale.Visible = true;
                pnlInventory.Visible = false;
            }
            else if (ddlProduct.SelectedIndex==2)
            {
                Label1.Text = ddlProduct.SelectedValue;
                pnlCashFlow.Visible = true;
                pnlProductSale.Visible = false;
                pnlInventory.Visible = false;
            }
            else 
            {
                Label1.Text = ddlProduct.SelectedValue;
                pnlCashFlow.Visible = true;
                pnlProductSale.Visible = false;
                pnlInventory.Visible = false;
            }
        }

Please help me to solve this problem.

[pritaeas]

int selectedIndex = ((DropDownList)sender).SelectedIndex;

Not sure, perhaps the combo needs to be inside the UpdatePanel for your code to work. Haven't tried.

[tarunap]

DropdownList should be inside UpdatePanel. Then the code will work.. And Trigger is also not necessary.