private void AddRecipient(Message.Recipient recipient)
 {
     if (Recipients.FirstOrDefault(x => x.EmailAddress.IsEqualTo(recipient.EmailAddress)) == null)
     {
         Recipients.Add(recipient);
     }
 }
 private void AddRecipient(Message.Recipient recipient)
 {
     if (!Recipients.Any(x => x.EmailAddress.IsEqualTo(recipient.EmailAddress)))
     {
         Recipients.Add(recipient);
         OnPropertyChanged(() => SendCommand);
     }
 }
        private void ContactSelected(Contact contact)
        {
            var recipient = new Message.Recipient
            {
                EmailAddress = contact.EmailAddresses[0]
            };

            AddRecipient(recipient);
        }
        private void DeleteRecipient(Message.Recipient recipient)
        {
            if (recipient == null)
            {
                return;
            }

            int pos = Recipients.IndexOf(x => x.EmailAddress.IsEqualTo(recipient.EmailAddress));

            Recipients.RemoveAt(pos);
            OnPropertyChanged(() => SendCommand);
        }
        private void UserSelected(User user)
        {
            var recipient = new Message.Recipient
            {
                EmailAddress = new EmailAddress
                {
                    Address = user.UserPrincipalName,
                    Name    = user.DisplayName
                }
            };

            AddRecipient(recipient);
        }
        private void DeleteRecipient(Message.Recipient recipient)
        {
            int pos = Recipients.IndexOf(x => x.EmailAddress.IsEqualTo(recipient.EmailAddress));

            Recipients.RemoveAt(pos);
        }