task attachment via Web Service


i am a Service Manager external user through Web Services .

In order to allow my application attaching some files to an SM Incident Task, a WS called "UpdateIncidentTask" was given to me.

In this WS, i have been informed that the following fields have to be filled as follows, in order to get the expected result:

UpdateIncidentTaskRequest.model.instance.TaskID : the ID of the IM Task, eg IM100000-001

UpdateIncidentTask_Request.model.instance.attachments.attachment0.href: The BASE64 code of the file to attach. 

UpdateIncidentTask_Request.model.instance.attachments.attachment0.name :  file.txt

UpdateIncidentTask_Request.model.instance.attachments.attachment0.type: application/octet-stream

UpdateIncidentTask_Request.model.instance.attachments.attachment0.action : add


But it still not working.

Could someone help me please.