This is code:

class XXXX

{

private BasicG2Gv1Client mBasicG2GClient;

private TransactionScope mTransactionScope;
        bool mTransactionError;
        bool mTransactionCompleted;

public void SendMessage(G2GMessageV1 message)
        {
            mBasicG2GClient = new BasicG2Gv1Client();
            mBasicG2GClient.SendMessageCompleted += new EventHandler<SendMessageCompletedEventArgs>(mBasicG2GClient_SendMessageCompleted);

            G2GMessageV11 g2gMessageV11
                = new G2GMessageV11(message.FileName, message.Reciever,
                    message.Subject, message.TimeStamp, message.Version, message.Content);

            TransactionOptions transOptions = new TransactionOptions();
            transOptions.IsolationLevel = IsolationLevel.RepeatableRead;
            transOptions.Timeout = new TimeSpan(0, 5, 0);

            mTransactionScope = new TransactionScope(TransactionScopeOption.RequiresNew, transOptions);

            mBasicG2GClient.SendMessageAsync(g2gMessageV11, mTransactionScope);
            mTransactionCompleted = true;
        }

private void mBasicG2GClient_SendMessageCompleted(object sender, SendMessageCompletedEventArgs e)
        {
            bool success = false;

            if (e.Error != null)
            {
                //log
                (e.UserState as TransactionScope).Dispose();
                OnSendMessageCompleted(success);
            }
            else
            {
                try
                {
                    success = true;
                }
                catch (Exception ex)
                {
                    //log
                    mTransactionError = true;
                }
                finally
                {

                    if (mTransactionCompleted && !mTransactionError)
                    {
                        (e.UserState as TransactionScope).Complete();
                        (e.UserState as TransactionScope).Dispose();

                    }
                    else
                    {
                        (e.UserState as TransactionScope).Dispose();

                    }
                    DisposeClient();

                    OnSendMessageCompleted(success);
                }
            }

        }

}

I used Web ASP.NET MVC client with Async SendController

Thanks