void bindDropDonw()
{
string ConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlDataAdapter da = new SqlDataAdapter("select empid from emp", ConnString);
DataTable dt = new DataTable();
da.Fill(dt); // Fill the dataset
DropDownList1.DataSource = dt;
DropDownList1.DataValueField = "empid";
DropDownList1.DataTextField = "empid";
DropDownList1.DataBind();
DropDownList1.Items.Insert(0, "-Select-");
}