private IObservable<LoginModel> GetLoginClicked(LoginModel model)
 {
     return LoginButton.GetClick()
         .Where(ev => model.IsValid()).Select(ev => model);
 }
 private IObservable<LoginModel> GetEnterKey(LoginModel model)
 {
     return PasswordInput.GetKeyDown()
         .Where(key => key.EventArgs.KeyCode == Keys.Enter)
         .Where(ev => model.IsValid()).Select(ev => model);
 }