A method organizing other calls to import customers into Mozu

ImportCustomers.cs

private System.Collections.Concurrent.ConcurrentDictionary<string,string> ImportCustomers(IEnumerable<Mozu.Api.Contracts.Customer.CustomerAccountAndAuthInfo> accountAuthCollection)
{
    var accountResource = new Mozu.Api.Resources.Commerce.Customer.CustomerAccountResource(_apiContext);
    var contactResource = new Mozu.Api.Resources.Commerce.Customer.Accounts.CustomerContactResource(_apiContext);

    var accountExternalIds = new System.Collections.Concurrent.ConcurrentDictionary<string, string>();

    Parallel.ForEach(accountAuthCollection, new System.Threading.Tasks.ParallelOptions() { MaxDegreeOfParallelism = 1 }, accountAuthInfo =>
    {
        var filter = string.Format("ExternalId eq '{0}'", accountAuthInfo.Account.ExternalId);

        var importedResultStatus = string.Empty;

        Mozu.Api.Contracts.Customer.CustomerAccount existingAcct = null;

        var existingAcctCollection = accountResource.GetAccountsAsync(filter: filter).Result;

        if (existingAcctCollection.Items.Count == 0)
        {
            try
            {
                existingAcct = accountResource.AddAccountAsync(accountAuthInfo.Account, "Id,ExternalId").Result;
                importedResultStatus = string.Format("Added-New-Account-Id:{0}", existingAcct.Id);

                var existingAcctAuthTicket = accountResource.AddLoginToExistingCustomerAsync(new Mozu.Api.Contracts.Customer.CustomerLoginInfo()
                {
                    EmailAddress = accountAuthInfo.Account.EmailAddress,
                    IsImport = accountAuthInfo.IsImport,
                    Password = accountAuthInfo.Password,
                    Username = accountAuthInfo.Account.UserName,
                }, existingAcct.Id).Result;

                foreach (var contact in accountAuthInfo.Account.Contacts)
                {
                    var existingContact = contactResource.AddAccountContactAsync(contact, existingAcct.Id, "Id").Result;
                }
            }
            catch (Exception ex)
            {
                importedResultStatus = "Error-Encountered";
            }

            accountExternalIds.TryAdd(existingAcct.ExternalId, importedResultStatus);
        }
    });

    return accountExternalIds;
}