Background: I'm trying to write an N-tier app and need to synchronize
datawindow controls and datastores.

DataWindowChanges changes0 = dsWork.GetChanges(); // length of blob = 433
dsWork.UpdateData(true, false); // update but don't reset status flags
DataWindowChanges changes1 = dsWork.GetChanges(); // length of blob 231 ???

SQLPreview is trapped and the code below is in it but shouldn't affect the
status flags. No data is changed in the trapped event.
e.Action = SqlPreviewAction.Skip; // Intellisense Help says TODO: (hmm,
not very reassuring)

Why would the blob be smaller after the update? The statuses should be
untouched and the blob should remain the same I would think. I have not
compared the results with a DataWindow, only a DataStore.