// 
IPoint pPoint = axMapControl1.ToMapPoint(e.x,e.y);
                    pGeometry = pPoint as IGeometry;//ӿڲѯ
                    IRgbColor pRgbColor = new RgbColorClass();//
                    pRgbColor.Red = 255;
                    pRgbColor.Green = 0;
                    pRgbColor.Blue = 0;
                    object symbol=null;
                    ISimpleMarkerSymbol pSimpleMarkerSymbol = new SimpleMarkerSymbolClass();
                    pSimpleMarkerSymbol.Color = pRgbColor;
                    pSimpleMarkerSymbol.Style = esriSimpleMarkerStyle.esriSMSDiamond;
                    pSimpleMarkerSymbol.Size = 20;
                    symbol = pSimpleMarkerSymbol;
                    axMapControl1.DrawShape(pGeometry,ref symbol);