setsaveasActivity

Question

I am trying to send an email to Order Contact and Order Owner and saving it as Completed Task(Activity History) against Order but Sent Email is saved against Contact's Activity History.How to save it against Order ?

    for(Order o:oList){
        Messaging.SingleEmailMessage OrderContactMail = new Messaging.SingleEmailMessage();
        OrderContactMail.setCcAddresses(new List<String>{o.Owner.Email}); 
        OrderContactMail.SaveAsActivity(true);
        String messageBody = 'some sample message';
               OrderContactMail.setSubject(subject);
               OrderContactMail.setHtmlBody(messageBody);
               OrderContactMail.setSaveAsActivity(true);
               OrderContactMail.setTargetObjectId(o.Contact__c);
               mails.add(OrderContactMail);
       }
     Messaging.sendEmail(mails);

From Docs :

setSaveAsActivity(Boolean)

Optional. The default value is true, meaning the email is saved as an activity. This argument only applies if the recipient list is based on targetObjectId or targetObjectIds. If HTML email tracking is enabled for the organization, you will be able to track open rates.

setTargetObjectId(ID)

Required if using a template, optional otherwise. The ID of the contact, lead, or user to which the email will be sent. The ID you specify sets the context and ensures that merge fields in the template contain the correct data.

Answer 1

You need to supply "what id" as well.

OrderContactMail.setWhatId(o.id);