Integrate Nexmo SMS API using C# in ASP.Net

I have this SMS API javascript code that i want to use in code behind method

please how do i create BULK SMS code with it.

var credentials = Credentials.FromApiKeyAndSecret(
    NEXMO_API_KEY,
    NEXMO_API_SECRET
    );

var nexmoClient = new NexmoClient(credentials);

var response = nexmoClient.SmsClient.SendAnSms(new Nexmo.Api.Messaging.SendSmsRequest()
{
    To = TO_NUMBER,
    From = NEXMO_BRAND_NAME,
    Text = "A text message sent using the Nexmo SMS API"
});