winform chart鼠标处显示mark

只需要在chart的GetToolTipText事件中增加下面的代码即可显示：

private void chart1_GetToolTipText(object sender, System.Windows.Forms.DataVisualization.Charting.ToolTipEventArgs e)
       {
           if (e.HitTestResult.ChartElementType == System.Windows.Forms.DataVisualization.Charting.ChartElementType.DataPoint)
           {
               int i = e.HitTestResult.PointIndex;
               System.Windows.Forms.DataVisualization.Charting.DataPoint dp = e.HitTestResult.Series.Points[i];
               e.Text = string.Format("({0:F3},{1:F3})", dp.XValue, dp.YValues[0]);
           }
       }