The IMsgStore::CompareEntryIDs method compares two entry identifiers to determine if they refer to the same entry within a message store. MAPI only passes this call to a service provider if the unique identifiers (UIDs) in both entry identifiers to be compared are handled by that provider.
HRESULT CompareEntryIDs(
ULONG cbEntryID1,
LPENTRYID lpEntryID1,
ULONG cbEntryID2,
LPENTRYID lpEntryID2,
ULONG ulFlags,
ULONG FAR * lpulResult
);
The IMsgStore::CompareEntryIDs method compares two entry identifiers belonging to the message store to determine whether they refer to the same object.
CompareEntryIDs is useful because an object can have more than one valid entry identifier; such a situation can occur, for example, after a new version of a message store provider is installed.
If CompareEntryIDs returns an error, do not take any action based on the result of the comparison. Instead, take the most conservative approach possible. CompareEntryIDs might fail if, for example, one or both of the entry identifiers contains an invalid MAPIUID.