protected RectangleF GetFittingRectangle()
{
RectangleF boundingRectangle = m_pieSlices[0].GetFittingRectangle();
for (int i = 1; i < m_pieSlices.Length; ++i) {
boundingRectangle = RectangleF.Union(boundingRectangle, m_pieSlices[i].GetFittingRectangle());
}
return boundingRectangle;
}