I added the TabPage dynamically into the a TabControl in a Windows Form application, and then I set its ToolTipText to some text, I assume the ToolTipText will be displayed when I move the move on the Tabpage, but it is shown up in fact.
The reason why the ToolTipText is not shown up is the ShowToolTips property in the host TabControl is set to False by default. So to display your ToolTipText, you have to set its value to True.
