union EcDoRpc_MAPI_REQ_UNION {
        struct Release_req mapi_Release;/* [case(op_MAPI_Release)] */
        struct OpenFolder_req mapi_OpenFolder;/* [case(op_MAPI_OpenFolder)] */
        struct OpenMessage_req mapi_OpenMessage;/* [case(op_MAPI_OpenMessage)] */
        struct GetHierarchyTable_req mapi_GetHierarchyTable;/* [case(op_MAPI_GetHierarchyTable)] */

...