In GH 6, after joining single curves into a polyline, CrvDom changes the domain such that each polyline segment is represented by an integer, ie. segment 1 = 0-1, segment 2 = 1-2, segment 3 = 2-3, etc.

In GH7, all else being equal, CrvDom changes the domain to be 0-length of polyline.

I relied on the GH 6 method to determine which polyline segment a point fell on. Does anyone know a workaround to get the same result as in GH 6? Thanks!

Using the RhinoCommon API method Rhino.Geometry.Curve.JoinCurves(IEnumerable<Curve>) produces the same differing results you have shown above on V6 vs V7 (must have been an API change).

This isn’t very difficult to do with standard components or a few lines of code.