DROPDOWN PROBLEM

I have a dropdown and the code below.
when i enable the line
DXmlFirmalar.Enabled =false;
it returns nothing
and when i disable
//DXmlFirmalar.Enabled =false;
it returns the value which is supposed..

I want to disable and getting the dropdown value either.

what is the problem ?
if (!Page.IsPostBack)

{

if (brand!="xx")

{

DXmlFirmalar.ClearSelection();

DXmlFirmalar.Items.FindByText(Firma).Selected = true;

DXmlFirmalar.Enabled =false;
}

}

else
{
XmlFirmalar = Request.QueryString["DXmlFirmalar"];

Response.Write (XmlFirmalar)

}