Problems accessing PreviousOrder from OrderSavingEventArgs

[kwesterlage]

I subscribed to an orderSavingEvent on the shell side for some lightweight order comparison logic (identifying new attachments), but when I attempt to access the PreviousOrder property of
the OrderSavingEventArgs I get a 'Specified method is not supported' exception'.

[BobRichards]

The previous order is only available on Server packages. In the shell package, you have to manually open the prior order version. This feature is made available on the Server since it is essentially available for "free" since Select gets the prior order version during the order save and typical order saving validations are done on the Server.

Depending on what you are attempting to do, you could to open the prior order version or perhaps save the current version of the necessary property(ies) in the Tags collection associated with the item so they are available during the next order save.