public static byte[] GetBytesFromImage(BitmapImage bmp)
        {
            byte[] imgArray = null;
            if (bmp != null)
            {
                imgArray = (new WriteableBitmap((BitmapImage)bmp)).Pixels.SelectMany(p => new byte[]
                {
                    (byte) p,
                    (byte) (p>>8),
                    (byte) (p>>16),
                    (byte) (p>>24)
                }).ToArray();
            }
            return imgArray;
        }

ServiceContacts1Client contacts = new ServiceContacts1Client();
               contacts.UpdateContactCompleted += new EventHandler<UpdateContactCompletedEventArgs>(contacts_UpdateContactCompleted);
               ServiceContacts contact = new ServiceContacts();
               ServiceContacts tempcont = new ServiceContacts();
               tempcont = (ServiceContacts)dataGrid1.SelectedItem;
               contact.idCont = tempcont.idCont;
               contact.first_name = firstName.Text;
               contact.last_name = lastName.Text;
               contact.mobile_phone = mobile.Text;
               contact.home_phone = homePhone.Text;
               if (contPhoto.Source != null)
               {
                   contact.photo = GetBytesFromImage((BitmapImage)contPhoto.Source);
               }
               contacts.UpdateContactAsync(contact);