[Solved] ASP.Net DropDownList returns same selected item

Please i have this drownlist with 4 items with the same list item value. Now i am trying to submit the selected value into the database but it keeps submiting the value of the first item on the dropdownlist which is NAND even when i choose logger, security or admin because they all have the same list item value.

But when i change the values it worked well.Please i want to be able to submit the selected item not the first item on the list even if it have the same list item value .

My Code

public partial class BioPluginWebApp_TRIAL : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Session["Vd"] = DropDownList1.SelectedItem;      
        Response.Write(Session["VD"]);
    }
}

<asp:DropDownList ID="DropDownList1" runat="server" Height="85px" 
    Width="439px">
    <asp:ListItem>SELECT</asp:ListItem>
    <asp:ListItem Value="600">NAND</asp:ListItem>
    <asp:ListItem Value="600">LOGGER</asp:ListItem>
    <asp:ListItem Value="600">SECURITY</asp:ListItem>
    <asp:ListItem Value="600">ADMIN</asp:ListItem>
</asp:DropDownList>