private async void SaveUser()
        {
            var isValidPassword = IsValidPassword();
            var isValidEmail    = IsValidEmail();

            if (isValidPassword && isValidEmail)
            {
                if (this.User == null)
                {
                    var user = new User()
                    {
                        Username = Username,
                        Email    = Email,
                        Password = Password,
                    };
                    await UsersDataStore.AddAsync(user);

                    userSaved?.Invoke(user);

                    await Task.Delay(2000);

                    Dialogs.Toast("User created: " + user.Username);
                }
                else
                {
                    var user = this.User;
                    user.Username = Username;
                    user.Email    = Email;
                    user.Password = Password;
                    await UsersDataStore.UpdateAsync(user);

                    userSaved?.Invoke(user);

                    await Task.Delay(1000);

                    Dialogs.Toast("Saved " + user.Username);
                }
            }
            else
            {
                var n         = Environment.NewLine;
                var allErrors = $@"
{String.Join($".{n}", await GetEmailErrors(Email))}
{String.Join($".{n}", GetPasswordErrors(Password) )}
{String.Join($".{n}", GetConfirmPasswordErrors(Password, ConfirmPassword))}";
                await Dialogs.AlertAsync(allErrors, "Error");
            }
            return;
        }
 async Task SaveUser(User user)
 {
     Users.Add(user);
     await UsersDataStore.AddAsync(user);
 }