you can add by using the query : you can add on pageload event of page.
but add in !ispostback event.
like.....
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
DataSet ds = new DataSet();
SqlDataAdapter myda = new SqlDataAdapter("Select field1 FROM Table", connection object);
myda.Fill(ds);
DropDown1.DataSource = ds;
DropDown1.DataValueField = "field1";
DropDown1.DataBind();
DropDown1.Items.Insert(0, new ListItem("Select One", "0"));
}
}
hope this will help you, if not then dear please post it.