using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        string aonTo = "DG-ASC-France-TBS@aon.com;";

         List<EmailAddress> result = aonTo.Contains(';') ? aonTo.Split(';').Select(x => new EmailAddress(x)).ToList()

                                                    : new List<EmailAddress>() { new EmailAddress(aonTo) };

        Console.WriteLine(result[0]);

    }

}

​

public class EmailAddress {

       public EmailAddress(string address)

        {

            if (address == null) throw new ArgumentNullException("address");

            Address = address;

        }

​

        public EmailAddress(string address, string displayName)

            : this(address)

        {

            DisplayName = displayName;

        }

​

        public string Address { get; private set; }

        public string DisplayName { get; set; }

​

        public override string ToString()

        {

            return string.Format("{0} <{1}>", DisplayName, Address);

        }

}