private void AttachSalesLiteratureItemToEmail(ICrmService service, salesliteratureitem sli, Guid EmailID, ref CrmNumber attachNo)
{
    // Create the request object to upload the file to CRM.
    activitymimeattachment upload = new activitymimeattachment();
    upload.activityid = new Lookup();
    upload.activityid.type = EntityName.email.ToString();
    upload.activityid.Value = EmailID;
    upload.attachmentnumber = attachNo;
    // and increment
    attachNo.Value++;
    // the contents:
    upload.filename = sli.filename;
    upload.filesize = sli.filesize;
    upload.mimetype = sli.mimetype;
    upload.body = sli.documentbody;
    // Upload the file to CRM.
    service.Create(upload);
    // done
}