Outlook Add-In: Event when selecting / changing subject line in new Mail. Visual Studio 2015 C# VSTO

Question

I want to create a Add-In for Outlook 2010 that shows a text field under the subject line of a new mail, when the user types something in.

Therefore I have to catch the event, when the subject line is selected and when content changes.

I googled quite a while, but I still have no idea how to programm it.

Any ideas / suggestions?

Answer 1

MailItem.PropertyChange event will fire only after the user tabs out of the Subject edit box. If you want to see the changes as the user types, your only choice is to hook the Subject edit box window proc and intercept the messages on the Windows API level.