Полезные знакомства

        private static Dictionary<string, List<string>> OptimizeContacts(List<string> contacts)
        {
            var dictionary = new Dictionary<string, List<string>>();
            if (contacts.Count!=0)
            {
                foreach (var contact in contacts)
                {
                    string[] nameAndEmail = Regex.Split(contact, ": ");

                    if (nameAndEmail[0].Length >= 1)
                    {
                        var key = nameAndEmail[0];
                        var email = "";
                        if (nameAndEmail[0].Length > 1)
                        {
                            email = nameAndEmail[1];
                        }
                        if (nameAndEmail.Length == 3)
                        {
                            email = nameAndEmail[1] + nameAndEmail[2];
                        }
                        if (key.Length == 1)
                            key = key.Substring(0, 1);
                        else if (key.Length > 1)
                            key = key.Substring(0, 2);

                        if (!dictionary.ContainsKey(key))
                            dictionary[key] = new List<string>();
                        else dictionary[key].Add(email);
                    }
                }
            }