Occurs just before the chart image map is rendered. Use this event to customize the map areas items.
Assembly: System.Web.DataVisualization (in System.Web.DataVisualization.dll)
Delete or modify map items that have automatically been created for a chart object; any data point, series, legend item or strip line object that has a non-empty Url, MapAreaAttributes or ToolTip property will have an associated map area object.
Add custom map areas that have a user-defined shape and coordinates.
The sender argument of type Chart is read-only.