编写arcgis代码时，无法显示线元素

[chuangwan]

IFeatureLayer fLayer = (IFeatureLayer)axMapControl1.get_Layer(1);
IFeatureLayer featureLyr = fLayer as IFeatureLayer;//将ILayer转换为IFeaturelayer，为了对图层上的要素进行编辑
IFeatureClass featCls = featureLyr.FeatureClass;
IFeatureClassWrite fClassWrite = (IFeatureClassWrite)featCls;//定义一个实现新增要素的接口实例，并将该实例作用于当前图层的要素集
IWorkspaceEdit wpEdit = (featCls as IDataset).Workspace as IWorkspaceEdit;//定义一个工作空间编辑对象，用于开启前图层的编辑状态
wpEdit.StartEditing(true);//开启编辑状态
wpEdit.StartEditOperation();//开启编辑操作

IPoint fromPoint = new ESRI.ArcGIS.Geometry.Point();
IPoint toPoint = new ESRI.ArcGIS.Geometry.Point();
IPolyline polyLine = new PolylineClass();

fromPoint.SpatialReference = this.axMapControl1.SpatialReference;
fromPoint.X = 600;
fromPoint.Y = 500;

toPoint.SpatialReference = this.axMapControl1.SpatialReference;
toPoint.X = 300;
toPoint.Y = 400;

polyLine.FromPoint = fromPoint;
polyLine.ToPoint = toPoint;


IGeometry geometry = polyLine;
IFeature feature = featCls.CreateFeature();
feature.Shape = geometry;
feature.set_Value(4, "10010");

feature.Store();
fClassWrite.WriteFeature(feature);
wpEdit.StopEditOperation();//停止编辑操作
wpEdit.StopEditing(true);//关闭编辑状态，并保存修改
this.axMapControl1.Refresh();//刷新地图

本人刚学Arcgis，各位帮忙看一下，这段代码画的线元素为什么不能显示？