IArea接口（计算多边形面积）

//利用IArea接口计算多边形面积

private Double MeasurePolygon(IPolygon pPolygon)
        {
            IArea pArea = (IArea)pPolygon;
            Double dArea = Math.Abs(pArea.Area);
            return dArea;
        }

//面积接口IArea
public double GetMeanArea(List<IFeature> Polygon)
        { 
        //求多边形的平均面积
            double dArea = 0;
            foreach (IFeature polygon in Polygon)
            {
                IArea pArea = polygon.Shape as IArea;
                dArea = dArea + pArea.Area;
            }
            MeanArea = dArea / Polygon.Count;
            return MeanArea;
        }