request.ServicePoint.BindIPEndPointDelegate = new BindIPEndPoint(this.BindIPEndPointCallback);
 ServicePointManager.FindServicePoint(requestUri).BindIPEndPointDelegate = new BindIPEndPoint(this.BindIPEndPointCallback);

private IPEndPoint BindIPEndPointCallback(ServicePoint servicePoint, IPEndPoint remoteEndPoint, int retryCount)
        {
            if (retryCount < 3)
            {
                return new IPEndPoint(IPAddress.Parse(this.ip), 0);
            }
            return new IPEndPoint(IPAddress.Any, 0);
        }