private async void LoginExecute(object obj)
        {
            if (SelectedUser != null)
            {
                DataContext.Instance.Iam.Nickname = SelectedUser.Nickname;
                DataContext.Instance.Iam.UserGuid = SelectedUser.UserGuid;
            }
            else
            {
                ApiClientService apiClientService = new ApiClientService();
                await apiClientService.RegisterMe(UserName);
            }

            CloseAction();
        }