「これらのパラメータを持つ MySQL ホストはありません」というエラーが表示されるのはなぜですか?

string MyConString = "SERVER=mysql7.000webhost.com;" +
            "DATABASE=a455555_test;" +
            "UID=a455555_me;" +
            "PASSWORD=something;";

MySqlConnectionStringBuilder conn_string = new MySqlConnectionStringBuilder();
conn_string.Server = "mysql7.000webhost.com";
conn_string.UserID = "a455555_test";
conn_string.Password = "a455555_me";
conn_string.Database = "xxxxxxxx";

using (MySqlConnection conn = new MySqlConnection(conn_string.ToString()))
using (MySqlCommand cmd = conn.CreateCommand())
{    //watch out for this SQL injection vulnerability below
     cmd.CommandText = string.Format("INSERT Test (lat, long) VALUES ({0},{1})",
                                    OSGconv.deciLat, OSGconv.deciLon);
     conn.Open();
     cmd.ExecuteNonQuery();
}