编写arcgis代码时，无法显示线元素

fly_sky

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？