C#+AE 添加图形标注

IMap pMap;
IActiveView pActiveView;
pMap = axMapControl1.Map;
pActiveView = pMap as IActiveView;
double gap = 0.5;
IPointCollection pPCol = new Polygon();
IPoint pPoint = null;
object ptmp = Type.Missing;
pPoint = new ESRI.ArcGIS.Geometry.Point();
pPoint.X = e.mapX - gap;
pPoint.Y = e.mapY + gap;
pPCol.AddPoint(pPoint, ref ptmp, ref ptmp);

pPoint.X = e.mapX - gap;
pPoint.Y = e.mapY - gap;
pPCol.AddPoint(pPoint, ref ptmp, ref ptmp);

pPoint.X = e.mapX + gap;
pPoint.Y = e.mapY - gap;
pPCol.AddPoint(pPoint, ref ptmp, ref ptmp);

pPoint.X = e.mapX + gap;
pPoint.Y = e.mapY + gap;
pPCol.AddPoint(pPoint, ref ptmp, ref ptmp);
ISimpleFillSymbol pSimpleFillSym;//用来实现填充
pSimpleFillSym = new SimpleFillSymbol();

IColor pColor = new RgbColor();
pColor.RGB = 255;
pSimpleFillSym.Color = pColor;
IFillShapeElement pPolygonEle;
pPolygonEle = new PolygonElement() as IFillShapeElement;
pPolygonEle.Symbol = pSimpleFillSym;
IElement pEle;
pEle = pPolygonEle as IElement;
pEle.Geometry = pPCol as IGeometry;

//将元素添加到Map对象中
IGraphicsContainer pGrapgicsContainer;
pGrapgicsContainer = pMap as IGraphicsContainer;
pGrapgicsContainer.AddElement(pEle, 0);
pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);