Polygone对象

   Polylgon对象是由一个或多个Ring对象的有序集合，它可以是由单个Ring 对象构
成，也可以使用多个Ring组成。Polygon通常用来代表有面积的多边形矢量对象，如行政
区，建筑物等。

组成Polygone的是Ring其中Ring可以分为Outer Ring(外环)和Inner  Ring(内环)
之分。外环和内环都是有方向的，它们的区别是外环的方向是顺时针的，内环的方向是逆时
针。

以下代码片段演示如何构建一个Polygon:
   private  object pMissing = Type.Missing;

         public  IGeometry GetPolygonGeometry()
        {
            const double RingVertexCount = 360;
            const double RingDegrees = 360.0;
            const double pOutRingRadius = 100;
            const double pInRingRadius = 40;
 
            IGeometryCollection pGeometryCollection = new PolygonClass();
 
 
 
                IPointCollection pOuterPointCollection = new RingClass();
                IPointCollection pInnerPointCollection = new RingClass();
 
              
                
 
                double pRotationAngleInRadians =
                       GetRadians(RingDegrees / RingVertexCount);
 
                for (int j = 0; j < RingVertexCount; j++)
                {
                                       pOuterPointCollection.AddPoint(ConstructPoint(pOutRingRadius
*Math.Cos(j*pRotationAngleInRadians),pOutRingRadius *Math.Sin(j*pRotationAngleInRadians)), 
ref pMissing, ref pMissing);
 
                    pOuterPointCollection.AddPoint(ConstructPoint (pInRingRadius * Math.Cos(j
* pRotationAngleInRadians), pInRingRadius * Math.Sin(j * pRotationAngleInRadians)), ref pMissing,
ref pMissing);
                           
                                  
                }

 
     ITopologicalOperator pTopologicalOperator =
            pGeometryCollection as ITopologicalOperator;
     pTopologicalOperator.Simplify();
     return pGeometryCollection as IGeometry;

     }
 
    
     private  double GetRadians(double pDecimalDegrees)
     {
         return pDecimalDegrees * (Math.PI / 180);
     }