/// <summary>
/// Returns a sequence of the major grid line coordinates.
/// </summary>
/// <param name="availableSize">The available size.</param>
/// <returns>A sequence of the major grid line coordinates.</returns>
protected override IEnumerable <UnitValue> GetMajorGridLineCoordinates(Size availableSize)
{
return(GetMajorTickMarkValues(availableSize).Select(value => GetPlotAreaCoordinate(value)).Where(value => ValueHelper.CanGraph(value.Value)));
}