protected void Page_Load(object sender, EventArgs e)
    {
        string serialKeyPath = Path.Combine(Server.MapPath("~/"), "SerialKeys.xlsx");
        List<string> serialKeys = ExelHelper.Instance.ReadSerialKeysFromExcel(serialKeyPath);

        SerialKeyManager mgr = new SerialKeyManager();

        foreach (string key in serialKeys)
        {
            mgr.Save(key);
        }
    }
 protected bool IsSeriralKeyExists(String key)
 {
     SerialKeyManager manager = new SerialKeyManager();
     return manager.IsKeyExists(key);
 }