private void mnuLegend_Click(Object sender, EventArgs e)
{
MenuItem _item = (MenuItem)sender;
Canvas _graph = (Canvas)_item.Tag;
plotData _plotData = getPlotData((string)_graph.Tag);
_plotData.displayLegend = !_plotData.displayLegend;
_item.IsChecked = _plotData.displayLegend;
plotSeries(_graph, _plotData, eZoom.FALSE, eRescale.FALSE);
}