Hello
Try as follws
REmove Enable ViewState and added OnSelectedIndexChange Event
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindDropDown();
}
}
protected void drp_New_SelectedIndexChanged(object sender, EventArgs e)
{
}
<asp:DropDownList ID="drp__New" OnSelectedIndexChanged=” drp_New_SelectedIndexChanged” runat="server" Width="200px" AutoPostBack="true">
</asp:DropDownList>
Hope this helpful