怎么在指定图层添加线元素（C#）

我是初学arcGis，请大家及时伸出援助之手啊 --------------------编程问答-------------------- 画线，首先得到线对象，要用到 IPointCollection 和    IPolyline 对象，

然后加载线元素IElement。

  /// <summary>
        /// 画线
        /// <param name="arrPointAll">点坐标数组</param>
        ///<returns></returns>
        private void DrawLine(ArrayList arrPointAll)
        {
            if (arrPointAll.Count <= 0)//点坐标数组不能为空
            {
                return;
            }

            if (activeView == null)
            {
                activeView = this.MapControl.ActiveView.FocusMap as IActiveView;
            }
            //删除以前的element
            DeleteOldElement(activeView.GraphicsContainer);

            // 获取IRGBColor接口
            IRgbColor color = new RgbColor();
            // 设置颜色属性
            color.Red = 255;
            color.Transparency = 255;

            //点
            IPoint pPoint = new PointClass();

            //线样式
            ISimpleLineSymbol lineSymbol = new SimpleLineSymbolClass();
            lineSymbol.Color = color;
            lineSymbol.Style = esriSimpleLineStyle.esriSLSInsideFrame;
            lineSymbol.Width = 1;

            //线元素
            ILineElement lineElement = new LineElementClass();
            lineElement.Symbol = lineSymbol;

            //创建线
            IPolyline m_Polyline = new PolylineClass();
            //点集合
            IPointCollection m_PointCollection = new PolylineClass();
            //点数组
            ArrayList arrPoint = new ArrayList();
            object missing = Type.Missing;
            foreach (object o in arrPointAll)
            {
                arrPoint = (ArrayList)o;
                pPoint.PutCoords(int.Parse(arrPoint[0].ToString()), int.Parse(arrPoint[1].ToString()));
                m_PointCollection.AddPoint(pPoint, ref missing, ref missing);
            }

            //QI for IPolyline
            m_Polyline = m_PointCollection as IPolyline;

            //放大地图

            //折线范围
            IEnvelope pEnvelope = m_Polyline.Envelope;
            //折线区域
            IArea pArea = pEnvelope as IArea;
            pPoint = pArea.Centroid;

            this.ChangeEnvelope(pPoint, 0.06, 0.06);
            //QI for IElement
            IElement element = lineElement as IElement;

            element.Geometry = m_Polyline;

            //加载线元素到地图
            activeView.GraphicsContainer.AddElement(element, 0);
            //Refresh the graphics
            activeView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);
        }

--------------------编程问答-------------------- 我试过了，没反应，地图上没有增加线 --------------------编程问答-------------------- IFeatureLayer pLayer = (IFeatureLayer)axMapControl1.get_Layer(0);//所要加的层
            IFeatureLayer pFeatureLyr = pLayer as IFeatureLayer;//将ILayer转换为IFeaturelayer，为了对图层上的要素进行编辑
            IFeatureClass pFeatCls = pFeatureLyr.FeatureClass;//定义一个要素集合，并获取图层的要素集合
            IFeatureClassWrite fr = (IFeatureClassWrite)pFeatCls;//定义一个实现新增要素的接口实例，并该实例作用于当前图层的要素集
            IWorkspaceEdit w = (pFeatCls as IDataset).Workspace as IWorkspaceEdit;//定义一个工作编辑工作空间，用于开启前图层的编辑状态
            IFeature f;//定义一个IFeature实例，用于添加到当前图层上   +
            w.StartEditing(true);//开启编辑状态
            w.StartEditOperation();//开启编辑操作

            IPoint point = new PointClass();
            point.SpatialReference = this.axMapControl1.SpatialReference;
            IGeometry geometry;
            point.X = 200;
            point.Y = 300;
            geometry = (IGeometry)point;

            IPoint point2 = new PointClass();
            point2.SpatialReference = this.axMapControl1.SpatialReference;
            IGeometry g2;
            point2.X = 400;
            point2.Y = 600;
            g2 = (IGeometry)point2;

            IPolyline line = new PolylineClass();
            line.SpatialReference = this.axMapControl1.SpatialReference;
            IGeometry gLine;
            line.FromPoint = point;
            line.ToPoint = point2;
            gLine = (IGeometry)line;

            f = pFeatCls.CreateFeature();//实例化IFeature对象，这样IFeature对象就具有当前图层上要素的字段信息
             IPolygon pPolygon = gLine as IPolygon;
            f.Shape = pPolygon;
            f.set_Value(4, "100010");//设置IFeature对象的索引是3的字段值
            f.Store();//保存IFeature对象
            fr.WriteFeature(f);//将IFeature对象，添加到当前图层上
            w.StopEditOperation();//停止编辑操作
            w.StopEditing(true);//关闭编辑状态，并保存修改
            this.axMapControl1.Refresh();//刷新地图
为什么不能在图层上显示线？？？

补充：.NET技术 ,  C#