cannot retrive dropdownlist selected value

Hi, im new to .net and having problem with a dropdownlist.
here is the code


  protected void addTagButton_Click(object sender, EventArgs e)
{
// extract css from stlysheet
Panel_tagStyleClass.Visible = true;
extractedCss.DataSource = builder.CssExtract(subdomain);
extractedCss.DataTextField = "Cssclass";
extractedCss.DataValueField = "Cssclass";
extractedCss.DataBind();
extractedCss.Items.Insert(0, new ListItem("Not configured", ""));
}
 
once tagadd clicked i load stylesheet and get clasess in style bound to dropdownlist together with save button
when save button clicked i try to ...