private void saveButton_Click(object sender, EventArgs e)
        {
            anAddress = new Address();
            anAddress.FirstName = firstNameTextBox.Text;
            anAddress.LastName = lastNameTextBox.Text;
            anAddress.Email = emailTextBox.Text;
            anAddress.PhoneNo = phoneNoTextBox.Text;

            bool varify=anAddressBook.CheckEmailAddress(emailTextBox.Text);

            if (varify)
            {
                bool check = anAddressBook.AddAddress(anAddress);

                if (check)
                {
                    MessageBox.Show("Address with this email already exists.");

                }
                else
                {
                    MessageBox.Show("Address saved successfully");
                    addressListDataGridView.DataSource = null;
                    addressListDataGridView.DataSource = anAddressBook.GetAllAddress();
                }
            }
            else
            {
                MessageBox.Show("Email address is not valid\nIt must contail only one @ and at least one(.)");
            }
        }
 public bool AddAddress(Address anAddress)
 {
     bool check = false;
     if (DoesThisAddressExist(anAddress))
     {
         check = true;
     }
     else
     {
         addressList.Add(anAddress);
     }
     return check;
 }
 private bool DoesThisAddressExist(Address address)
 {
     foreach (Address anAddress in addressList)
     {
         if (anAddress.Email == address.Email)
         {
             return true;
         }
     }
     return false;
 }