ArcObjects: How to get the midpoint of a set of polylines?

Question

How can I find the midpoint (along the curve) of a set of polylines using ArcObjects?

Answer 1

There are probably several ways to do this but here is one that should work:

1. Union the input polylines into a single geometry using ITopologicalOperator.Union
2. Cast the resulting geometry to ICurve and call ICurve.QueryPoint with DistanceAlongCurve = 0.5 and asRatio = true. Note: this method will likely throw an error if the geometries are disjointed.
3. Do what you need with the output IPoint