title: Can I prevent the WPF ToolTip from showing up from inside the ToolTipOpening event handler?
body: <p>I have a canvas with MANY shapes in it and I want each one of them to display a string ToolTip. In order to save some memory I wanted to set the ToolTip value when the tooltip opens, so I set the ToolTip to be an empty string on every shape initially and then I set the real value of it just before it becomes visible (in the ToolTipOpening event handler that is). However, sometimes the ToolTip I set in the ToolTipOpening event handler is an empty string and I don't want the ToolTip to show up in those cases.</p>
  
  <p>Is there something I can do from within the ToolTipOpening event handler to hide it? Or perhaps an easy way to know when the mouse pointer stays over a shape for some time (in order to show a ToolTip programmatically)?</p>