/// <summary>
        /// Add EmailAddressTextBox.Text to List when AddToListButton on OnClick
        /// </summary>
        /// <param name="sender">Sender Parameter</param>
        /// <param name="e">Event Parameter</param>
        private void AddToListButtonOnClick(object sender, RoutedEventArgs e)
        {
            if (Regex.IsMatch(EmailAddressTextBox.Text, @"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z", RegexOptions.IgnoreCase))
            {
                var emailAddress = new CustomEmailAddress()
                {
                    Email = EmailAddressTextBox.Text
                };

                vm.Add(emailAddress);
                EmailAddressTextBox.Clear();
            }
            else
            {
                MessageBox.Show("Please use a valid Email format");
            }
        }
 public void Add(CustomEmailAddress emailAddress)
 {
     emailAdresses.Add(emailAddress);
 }