public async Task AddContact(ExchangeClientDemo.Models.MyContact contact)
        {
            var client = await EnsureClientCreated();

            var newContact = new Microsoft.Office365.Exchange.Contact {
                GivenName      = contact.GivenName,
                Surname        = contact.Surname,
                CompanyName    = contact.CompanyName,
                EmailAddress1  = contact.EmailAddress1,
                BusinessPhone1 = contact.BusinessPhone1,
                HomePhone1     = contact.HomePhone1
            };
            await client.Me.Contacts.AddContactAsync(newContact);
        }
        public async Task UpdateContact(ExchangeClientDemo.Models.MyContact contact)
        {
            string id = contact.Id;

            var client = await EnsureClientCreated();

            var contactToUpdate = await client.Me.Contacts.GetById(id).ExecuteAsync();

            contactToUpdate.GivenName      = contact.GivenName;
            contactToUpdate.Surname        = contact.Surname;
            contactToUpdate.CompanyName    = contact.CompanyName;
            contactToUpdate.EmailAddress1  = contact.EmailAddress1;
            contactToUpdate.BusinessPhone1 = contact.BusinessPhone1;
            contactToUpdate.HomePhone1     = contact.HomePhone1;

            await contactToUpdate.UpdateAsync(true);

            await client.Context.SaveChangesAsync();
        }