如何在AO中将椭圆弧转换成椭圆面

<P>本人需要在程序中实现，添加新的图层，并画一个椭圆，可以填充的，我的想法是先画一个椭圆弧，然后获得椭圆弧的点集，将其转换成polygon格式，不知道可行麽？因为初接触gis，可能很多想法比较幼稚，希望有大侠不吝赐教。下面是我写的转换函数</P>
<P>但是每次执行到红色部分就会显示无效的类型转换，geometry是已经画好的椭圆弧</P>
<P> Private Function createPolygon(ByVal geometry As IEllipticArc) As Polygon<BR>        Dim pGonColl As IGeometryCollection<BR>        Dim pPointColl As IPointCollection<BR>        Dim i As Integer<BR>        pGonColl = New Polygon<BR>        <FONT color=#f73809>pPointColl = geometry</FONT><BR>        pGonColl.AddGeometry(pPointColl)<BR>        Return pGonColl<BR>    End Function</P>

<P> Private Function createPolygon(ByVal geometry As IEllipticArc) As Polygon<BR>        Dim pGonColl As IPointCollection<BR>        pGonColl = New Polygon<BR>        Dim pPointColl As IPointCollection<BR>        pPointColl = New Polygon<BR>        Dim i As Integer<BR>        Dim pSeg As ISegment<BR>        pSeg = geometry<BR>        Dim pPolyline As ISegmentCollection<BR>        pPolyline = New Polyline<BR>        pPolyline.AddSegment(pSeg)<BR>        pPointColl = pPolyline</P>
<P><BR>        For i = 0 To pPointColl.PointCount - 1<BR>            pGonColl.AddPoint(pPointColl.Point(i))<BR>        Next<BR>        Return pGonColl<BR>    End Function<BR>我修改成如上</P>
<P>发现椭圆弧的点集里只有一个点，起点和终点重合，没有其他描述信息了，这可怎么办啊？</P>