Creating and Sending SMS messages using the Esendex .Net SDK - Full details here: http://developers.esendex.com/

CreateAndSendSMS.cs

using com.esendex.sdk;
using com.esendex.sdk.messaging;

...

var credentials = new EsendexCredentials(USERNAME, PASSWORD);
var messagingService = new MessagingService(true, credentials);
try
{
    var message = new SmsMessage("447123456789", "This is a test message...", "<myAccountReference>");
    var result = messagingService.SendMessage(message);

    Console.WriteLine("Sent Message Batch Id: {0}", result.BatchId);

    foreach (var messageId in result.MessageIds)
    {
        Console.WriteLine("Message Uri: {0}", messageId.Uri);
    }
}
catch (WebException ex)
{
    Console.Write(ex.Message);
}