When smart labels are enabled, the Chart control first attempts to reposition an overlapping data point label near the data point itself. If it fails, the Chart control then moves the data point label to a valid free space and draws a callout line to link the label with the data point.

The callout line's visual attributes, which include color, line style, and line width, are programmable. In addition, the CalloutStyle and CalloutLineAnchorCap properties determine the decorations at the end of the callout line.