手工画扇型(1)

在MapObject控件的基础上画扇型，保存画的轨迹，并得到扇型内的数据。由于MapObject不提供画扇型的Track方法，所以只能借助System.Drawing.Graphic来画，正好Graphic有方法DrawPie()。
1.先考虑如何画
  用户第一次点击MapObject上任意一点时，设为圆心，第二此点击时候，便确立半径，接着用户可以拉动鼠标到任意位置，呈现出扇型。
如果角度大于180，那么将画出相反方向的扇型。
为了让用户有操作体验，也就是在确立圆心时候，拉动鼠标时候，产生一条线以此来提示用户，那么可以借助MapObject中画线方法来进行。
在mapojbect_MouseDownEvent事件下

//定义类成员变量
        private ESRI.MapObjects2.Core.Line radiusLine;

        private ESRI.MapObjects2.Core.Points collectPoints;
private int sumTotal = 0;//控制点的数量
if(e.button == 1)
{
  StartSector（e.x,e.y);
}
        /// <summary>
        /// start sector
        /// </summary>
        /// <param name="pointX"></param>
        /// <param name="pointY"></param>
        private void StartSector(int pointX, int pointY)
        {
            if (radiusLine == null)
            {
                radiusLine = new LineClass();
            }
            if (collectPoints == null)
            {
                collectPoints = new PointsClass();
            }
            ESRI.MapObjects2.Core.Point anyPoint = axMap.ToMapPoint(pointX,pointY);
            // use radiusLine to draw variety line.
            if (collectPoints.Count == 2)
            {
                // because point has increased on mouse move event.
                collectPoints.Remove(1);
                radiusLine.Parts.Remove(1);
            }
            collectPoints.Add(anyPoint);
            radiusLine.Parts.Add(collectPoints); //draw a fixed line.
            sumTotal++;

            if (collectPoints.Count == 2 && sumTotal == 2)
            {
                //store two points. 
                StoreSectorRadiusPoint(collectPoints.Item(0),collectPoints.Item(1));
            }
           
            if (sumTotal == 3)
            {    
                ClearSectorIdentity();
                SectorSelect(anyPoint);
            }
        }

        /// <summary>
        /// clear sector indentifier to do next. v3.1
        /// </summary>
        public void ClearSectorIdentity()
        {
            sumTotal = 0;
            int pTotal = 0;
            if (collectPoints != null)
            {
                pTotal = collectPoints.Count;
                for (int i=0 ; i<pTotal; i++)
                {
                    collectPoints.Remove(0);
                }
            }
            if (radiusLine != null)
            {
                pTotal = radiusLine.Parts.Count;
                for (short i=0 ; i<pTotal; i++)
                {
                    radiusLine.Parts.Remove(0);
                }
                axMap.CtlRefresh();
            }
            
        }

        /// <summary>
        /// move mouse to draw line    
        /// </summary>
        /// <param name="pointX"></param>
        /// <param name="pointY"></param>
        private void MoveDrawLine(int pointX,int pointY)
        {
            axMap.Refresh();
            if (collectPoints.Count > 1)
            {
                collectPoints.Remove(1); // just two points
            }
            if (radiusLine.Parts.Count > 1)
            {
                radiusLine.Parts.Remove(1);
            }
            ESRI.MapObjects2.Core.Point anyPoint = axMap.ToMapPoint(pointX,pointY);
            collectPoints.Add(anyPoint);
            radiusLine.Parts.Add(collectPoints); //draw a line.
        }

        /// <summary>
        /// determine three point and show to do next.
        /// </summary>
        /// <param name="thirdPoint"></param>
        private void SectorSelect(ESRI.MapObjects2.Core.Point thirdPoint)
        {
            axMap.MousePointer = MousePointerConstants.moHourglass;
            try
            {
                mapTool.SectorSelect(thirdPoint);
                //stat and show form
                StartSelection(true);
            }
            catch(Exception ep)
            {
                IdgpTrace.IdgpTraceError("RectSelect error. " + ep.Message,ModuleName.GISWINDOW);
            }

        }

另外在MouseMoveEvent事件（主要是为画线，因为移动鼠标可以确认一点，那么可以就可以画线）

            if ( sumTotal >= 1)
            {
               if (sumTotal == 1) // draw line
               {
                  MoveDrawLine(e.x,e.y);
               }
               else  // draw sector
               {
                  ESRI.MapObjects2.Core.Point varietyPoint = axMap.ToMapPoint(e.x,e.y);
                 //draw sector            
                 DrawVarietySector(axMap,varietyPoint);                  
               }
            }

画线必须使用drawShape()方法，该方法必须在AfterTrackingLayerDraw这样的事件下写

                if (radiusLine.Parts.Count == 2)   //draw line
                {
                    ESRI.MapObjects2.Core.Symbol symLine = new SymbolClass();
                    symLine.SymbolType = ESRI.MapObjects2.Core.SymbolTypeConstants.moLineSymbol;
                    symLine.Color = System.Convert.ToUInt32(ESRI.MapObjects2.Core.ColorConstants.moBlack);
                    axMap.DrawShape(radiusLine,symLine);
                }