Selection rendering is a special render mode internally used by the component to locate objects in the chart given 2D coordinates relative to the component viewport. This render mode is not as computationally expensive as the normal rendering because it automatically discards a lot of options such as lighting, jittering, antialiasing, image filters and so on. In practice there are interactivity modes that require a lot of selection requests - for example when you move the mouse over the control and tooltips are turned on or when you need to change the mouse cursor depending on the underlaying chart object. This is why internally the component caches selection rendering and when there are subsequent interactivity requests the component refers to the internal cache rather than rendering the whole chart again. The component automatically decides when the selection cache is outdated, but you can force its recreation by calling the refresh method:

chartControl.Refresh();

chartControl.Refresh()

In some cases however keeping a selection cache is not desirable - for example when the component state changes frequently, when there are few interactivity requests or when you want to reduce the memory footprint of the control. To turn off the selection cache you must modify the CacheSelectionRendering property of the NChart object:

chart.CacheSelectionRendering = false;

chart.CacheSelectionRendering = False