Can't programmatically set follow up on Outlook 2016 taskitem in C#

Question

In Outlook 2016 (and I assume previous versions) you are able to right-click a task and select Follow-up, and then choose when you'd like to have the item followed up.

I am trying to do the same thing programmatically in an Outlook Addin using VSTO in Visual Studio 2015.

I can see in the link below that you can use the method MarkAsTask on several item types (for instance, mailitem) but the method doesn't exist for TaskItems.

So how can I programmatically emulate the behaviour that exists in the Outlook client?

https://msdn.microsoft.com/VBA/Outlook-VBA/articles/mailitem-markastask-method-outlook

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Edit: We've already tried simply changing the start/end date on the task, and it doesn't have the same effect as clicking Follow Up in Outlook. Perhaps some history would be good here, to explain what we are actually trying to achieve.

We set up a SharePoint Task List to hold a list of tasks we're all working on that other users can see. This works great, but the ultimate aim was to have this show in the To-Do-Bar as a type of "dashboard". Unfortunately, we soon realised tasks assigned to other users don't appear in the To-Do-Bar.

But I since accidentally discovered, if you click a task assigned to another user, and click "Follow-up" and choose No Date (or any date range), it WILL in fact appear in the To-Do-Bar. But of course we don't want to have to do this constantly for tasks to appear in the To-Do-Bar, so I thought I'd write a tiny add-in to regularly do this programmatically. But I cannot seem to emulate this unintended effect of clicking "Follow-up" in the Outlook client with VSTO.

Answer 1

Clicking "Follow up" on a task simply changes the Due Date and Start Date. You can see the changes in OutlookSpy (I am its author - click IMessage button to see all available properties).