Gets or sets the vertical position of the LineMarker relative to the plot area. Its value range is (0, 1). If set this value,then the line marker's vertical position is fixed. If the value is null or undefined and interaction is set to LineMarkerInteraction.Move or LineMarkerInteraction.Drag, the vertical position of the LineMarker is calculated automatically based on the pointer's position.

public double VerticalPosition {get; set;}