The DoesAllowDuplicates method is received by the server in an RPC_REQUEST packet. In response, the server returns whether (through a Boolean) the IAppHostElementCollection from which the specified IAppHostCollectionSchema was retrieved allows duplicate IAppHostElement objects to exist in the collection. The concept of "duplicate" is implementation-specific.

 [propget] HRESULT DoesAllowDuplicates(
   [out, retval] VARIANT_BOOL* pfAllowDuplicates
 );

pfAllowDuplicates: The Boolean value that represents whether duplicates are supported.

Return Values: The server MUST return zero if it successfully processes the message that is received from the client. If processing fails, the server MUST return a nonzero HRESULT code as defined in [MS-ERREF]. The following table describes the error conditions that MUST be handled and the corresponding error codes. A server MAY return additional implementation-specific error codes.

Return value/code	Description
0X00000000 NO_ERROR	The operation completed successfully.
0X80070057 ERROR_INVALID_PARAMETER	One or more parameters are incorrect or null.