see on GitHub

Operations : Attachments : How to Delete an Attachment

This operation is used to delete an attachment from a document.

Syntax

public DeleteAttachmentOperation(string documentId, string name, string changeVector = null)

Parameters
documentId string ID of a document containing an attachment
name name Name of an attachment
changeVector string Entity changeVector, used for concurrency checks (null to skip check)

Example

store.Operations.Send(new DeleteAttachmentOperation("orders/1-A", "invoice.pdf"));