ARCMAP中显示线的方向：COGO工具栏中
ARCMAP中VBA编写的宏可以添加到自定义工具栏中。当作按钮使用。
复杂线段可能存在不相连的情况，线段由分离的不同线段组成，在合并为一条线段时，需将线的shape转为GeometryCollection，以此遍历GeometryCollection中的Geometry来获取不同的部分。GeometryCollection的具体描述如下：
A Collection of Geometry parts. For Multipoints, TriangleFans, and
TriangleStrips, the Geometry parts are Points. For Polylines, the
Geometry parts are Paths. For Polygons, the Geometry parts are Rings.
For MultiPatches, the Geometry parts are TriangleFans, TriangleStrips,
or Rings. For GeometryBags, the Geometry parts are any IGeometry
object.