画圆并将圆（线）转换成区域

// 定义圆的中心点

IPoint point = new PointClass();

point.X = 119.302302426605;

point.Y = 26.0989696929962;

// 半径

double radius = 0.001;

// 圆构造器

ICircularArc circularArc = new CircularArcClass();

IConstructCircularArc constructCircularArc = circularArc as IConstructCircularArc;

// 开始画圆

constructCircularArc.ConstructCircle(point, radius, true);

// 线集合 将集合实例化为闭合线的对象

ISegmentCollection pPolyline;

pPolyline = new RingClass();

object Missing1 = Type.Missing;

object Missing2 = Type.Missing;

// 将圆（线）添加到线集合

pPolyline.AddSegment(circularArc as ISegment, ref Missing1, ref Missing2);

IRing pRing = pPolyline as IRing;

// 将线集合闭合

pRing.Close();

IGeometryCollection pPolygon;

pPolygon = new PolygonClass();

// 将闭合后的线转换为区域

pPolygon.AddGeometry(pRing, ref Missing1, ref Missing2);