populating a dropdown from database using javascript webservice

 SqlConnection conn;


    [System.Web.Services.WebMethod]
    public static List<Country> GetCountries()
    {
        string constr = "................";
        conn = new SqlConnection();
        conn.ConnectionString = constr;
        conn.Open();
        string sql = "Select distinct Countries from table";
        SqlDataAdapter da = new SqlDataAdapter(sql, conn);
        DataTable dt = new DataTable();
        da.Fill(dt);
        string[] items = new string[] {
                (dt.Rows.Count - 1)};
        int i = 0;
        foreach (DataRow dr in dt.Rows)
        {
            items.SetValue(dr["Countries"].ToString(), i);
            i++;
        }
        return items;
    }



    public class Country
    {
        private string _name;
        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        private string _id;
        public string Id
        {
            get { return _id; }
            set { _id = value; }
        }
    }

You cannot use a page variable inside static method.

Declare conn object inside the WebMethod