title: How do I change and display a tooltip on a chart in c# when the mouse hovers over a bar?
body: <p>I have a <code>System.Windows.Forms.DataVisualization.Charting.chart</code> and I want to show some information about a bar on the chart when you hover over it.
  But I can't see where to set a tooltip.</p>
  
  <p>I can set this <code>chart3.Series[0].ToolTip = "hello world";</code></p>
  
  <p>but  how do I pick up which <code>x</code> or <code>y</code> value I am hovering over in order to modify the text?</p>