private async void SignUp() { bool result = await UsersAPI.RegisterPostRequest(Email, Password); if (result) { if (RememberMe) { string[] dataToSave = AuthenticationUser.GetInstance().SaveUser(); ProcessData.SaveData(dataToSave); } _goToApp.Invoke(); } else { string caption = "Register Error"; string text = "Register Error. Invalid Email or Password"; MessageBoxImage icon = MessageBoxImage.Error; MessageBoxButton button = MessageBoxButton.OK; MessageBox.Show(text, caption, button, icon); } }