The SCardIO_Request structure represents the data to be prepended to a Transmit command (for more information, see section 3.1.4.35).

 typedef struct _SCardIO_Request {
   unsigned long dwProtocol;
   [range(0,1024)] unsigned long cbExtraBytes;
   [unique] [size_is(cbExtraBytes)] byte *pbExtraBytes;
 } SCardIO_Request;

dwProtocol: The protocol in use. Possible values are specified in section 2.2.5.

cbExtraBytes: The number of bytes in the pbExtraBytes field.

pbExtraBytes: Request data.