Office Add-in does not appear on taskbar

I am writing a VSTO add-in for PowerPoint 2007/2010, which opens its own Form.

If powerpoint has only one presentation open, opening the Add-In shows it on the Taskbar. However, when Powerpoint already has more than one presentation op开发者_运维知识库en the add-in does not show on the taskbar, but still appears in the Alt+Tab list.

How can I have the add-in window appear on the taskbar always, regardless of number of open presentations?

BTW, I checked and both Application.ShowWindowsInTaskbar and ShowInTaskbar are true, even when the add-in window does not appear on the taskbar.

I found the solution here: How to make window appear in taskbar?