The IsDiffGram causes only changes to be sent to the XML file?



>Kevin,
>I don't know really. Probably it means attached XML stays as is but only the ToXML(...,lChangesOnly) outputs diffgram.
>Cetin
>
>>Thanks! This example is exactly what I was looking for.
>>
>>The help file says "Setting the IsDiffGram property does not actually
>>alter the associated XML document."
>>
>>I'm not sure I understand this property. Can you elaborate?
>>
>>Thanks Cetin!
>>
>>
>>
>>
>>>Yes and no. Depends on version. Under VFP9 you have the luxury doing this with XMLAdpater class. The diffgram I pasted is from VFP7. Here is a sample for VFP9 that both creates the diffgram (might be your COM1) and updates from XML diffgram (might be your COM2):
>>>

>>>LOCAL lcDiffXML
>>>lcDiffXML = GetDiffGram() && COM1 creates diff.
>>>UpdateFromDiffgram(m.lcDiffXML) && COM2 gets XML
>>>
>>>
>>>PROCEDURE GetDiffGram
>>>USE _samples+"\data\customer"
>>>CURSORSETPROP("Buffering",5,'customer')
>>>BROWSE TITLE "Modify on site 1"
>>>
>>>* Create diffgram xml
>>>LOCAL lcChanges, oAdapter
>>>oAdapter = CREATEOBJECT('xmlAdapter')
>>>oAdapter.AddTableSchema('customer')
>>>oAdapter.IsDiffgram = .T.
>>>oAdapter.ToXML('lcChanges','',.f.,.t.,.t.)
>>>* Closing data just for sampling
>>>USE IN 'customer'
>>>RETURN m.lcChanges
>>>
>>>PROCEDURE UpdateFromDiffgram(tcDiffGram)
>>>LOCAL oAdapter
>>>* just for sampling using a different alias
>>>USE _samples+'data\customer' ALIAS myCustomer
>>>* we don't want to save when we are sampling only
>>>CURSORSETPROP("Buffering",5,'myCustomer')
>>>BROWSE TITLE 'Before applying diffgram'
>>>
>>>oAdapter = CREATEOBJECT('xmlAdapter')
>>>oAdapter.LoadXML(m.tcDiffGram,.f.)
>>>oAdapter.Tables(1).Alias = 'myCustomer'
>>>oAdapter.Tables(1).ApplyDiffgram()
>>>BROWSE TITLE 'After applying diffgram'
>>>

Too much hardcoding in there but this is a sample:)
>>>PS: AFAIK you also work with .Net and you would like to know XMLAdapter is friendly with .Net datasets and diffgrams (also VFPOLEDB have as added support).
>>>Cetin
>>>
>>>>Do I understand that I must store the changes back to the database myself? How is this
>>>>done? There could be any number of records and field changed. Is there any way to do
>>>>this automatically?
>>>>
>>>>
>>>>
>>>>>XmlUpdateGram() function creates an updategram (needs multilocks and buffering). That is it only includes updated/inserted/deleted records as updgram:before and after records. Suppose you updated customer table and changed company field, deleted ANATR and inserted NEWCUS. XmlUpdateGram('customer') produces an output like:
>>>>>

>>>>><?xml version = "1.0" encoding="Windows-1252" standalone="yes"?>
>>>>><root xmlns:updg="urn:schemas-microsoft-com:xml-updategram">
>>>>>	<updg:sync>
>>>>>		<updg:before>
>>>>>			<customer>
>>>>>				<cust_id>ALFKI</cust_id>
>>>>>				<company>Alfreds Futterkiste</company>
>>>>>* other fields here
>>>>>			</customer>
>>>>>		</updg:before>
>>>>>		<updg:after>
>>>>>			<customer>
>>>>>				<cust_id>ALFKI</cust_id>
>>>>>				<company>Alfreds Futterkiste-Updated</company>
>>>>>* other fields here
>>>>>			</customer>
>>>>>		</updg:after>
>>>>>		<updg:before>
>>>>>			<customer>
>>>>>* all fields here - unmodified
>>>>>			</customer>
>>>>>		</updg:before>
>>>>>		<updg:after/>
>>>>>		<updg:before/>
>>>>>		<updg:after>
>>>>>			<customer>
>>>>>				<cust_id>NEWCUS</cust_id>
>>>>>* other fields here
>>>>>			</customer>
>>>>>		</updg:after>
>>>>>	</updg:sync>
>>>>></root>
>>>>>

Instead of receiving the whole table diffgram approach only gets 'differences' IOW. On receving side you have to process this yourself however (ie: XMLDocument). VFP9 CA and XMLAdapter might help you to work with them in an easier way. Check www.prenia.com for samples.
>>>>>Cetin
>>>>>
>>>>>
>>>>>>The reason I'm using COM is because I will need to update the
>>>>>>application piece by piece. I don't want everything compiled
>>>>>>into one big EXE.
>>>>>>
>>>>>>Can you elaborate on the DiffGram option?
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Hmm that in turn would bring up other questions. Ways to go are more than one and which one to choose depends. ie: One scenario:
>>>>>>>
>>>>>>>Instead of CursorToXml and XmlTocursor you might choose ADO and pass an ADO recordset instead.
>>>>>>>Another one is to pass a diffgram instead of all rows using CursorToXML and XMLToCursor.
>>>>>>>Yet another one might be passing just an array of records that are updated/added/deleted with flags.
>>>>>>>
>>>>>>>Actually first I would think of "do I really want to talk between COM objects or even do I want a single COM object in my application" - sounds like I don't like COM objects:) Really I don't, too much problems with them for me (call it DLL hell, security etc etc).
>>>>>>>
>>>>>>>If one of them can connect to data why would other one cannot and a need for 2 evils?
>>>>>>>Cetin
>>>>>>>
>>>>>>>>Thanks. This brings up another question.
>>>>>>>>
>>>>>>>>I want to use CURSORTOXML() and XMLTOCURSOR() to pass data to and
>>>>>>>>from COM objects.
>>>>>>>>
>>>>>>>>Once I make changes to data and convert it to XML, and after I use
>>>>>>>>XMLTOCURSOR() to create a cursor, whats the best way to update the
>>>>>>>>database?
>>>>>>>>
>>>>>>>>I am using a VFP database now, with possible plans later to convert
>>>>>>>>to SQL Server.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>>For the 'nOutputFormat', 'nFlags', 'cSchemaName', 'cSchemaLocation', and 'cNameSpace'
>>>>>>>>>>parameters, are there any standards as far as what settings I should use?
>>>>>>>>>>
>>>>>>>>>>I am only using the command to pass data back & forth between COM objects.
>>>>>>>>>
>>>>>>>>>If there were standards there wouldn't be flags;)
>>>>>>>>>nOutputFormat: 2 or 3 are my favorites. More compact.
>>>>>>>>>nFlags: 1 to make it compact.
>>>>>>>>>For others it depends. Probably "1" inline schema would be good.
>>>>>>>>>
>>>>>>>>>With these settings:
>>>>>>>>>CursorToXml('myAlias','myMemvar',2,1,0,"1")
>>>>>>>>>would create a compact XML with inline schema and store in m.myMemvar and IMHO is good for your need.
>>>>>>>>>Cetin