mesh edge topology: how does it work? how is that sorted when offseting a mesh?

Hi to everybody,

I am creating a solid mesh with c# just offseting topside and bottomside a central mesh.

When I am doing this the vertex and face list index remain consistent with the original central surface, but this is not happening with the edge mesh list!

In fact when I want to create mesh faces (the side mesh faces to close the boundaries surfaces) I can see (and I have tested/x2 checked within GH), that the corrispondent top edge and bottom edge of a determinated face are not coincident.

How can I assign a consistent index list to the top and bottom mesh edge list?

How the edge topology is assigned?

I post here the code, FYI, even I do not think that can help to find the problem.

And 2 screenshot to show you the problem.

            double thickness = new double();
            if (!DA.GetData(0, ref thickness)) return;
            
            Mesh baseMesh = new Mesh();
            if (!DA.GetData(1, ref baseMesh)) return;

            List<Plane> localCSPlanes = new List<Plane>();
            if (!DA.GetDataList<Plane> (2, localCSPlanes)) return;

            List<Mesh> solidMesh = new List<Mesh>();
            List<Point3d> meshFaceCenterPlus = new List<Point3d>();
            List<Point3d> meshFaceCenterMinus = new List<Point3d>();
            List<Plane> localCSPlanesPlus = new List<Plane>();
            List<Plane> localCSPlanesMinus = new List<Plane>();
            List<Line> edgeMeshPlusLine = new List<Line>();
            List<Line> edgeMeshMinusLine = new List<Line>();

            Mesh offsetPlus = baseMesh.Offset(0.5*thickness, false);
            Mesh offsetMinus = baseMesh.Offset(-0.5 * thickness, false);

            Mesh recMesh = new Mesh();

            solidMesh.Add(offsetPlus);
            solidMesh.Add(offsetMinus);
            
            //This for-cycle creates a index-consistent list of plus-offset mesh face center points and local coordinate system mesh planes.
            int nFcsPl = offsetPlus.Faces.Count;
            int nEdg = offsetPlus.TopologyEdges.Count;

            for (int i = 0; i <= nFcsPl - 1; i++)
            {
                meshFaceCenterPlus.Add(new Point3d(offsetPlus.Faces.GetFaceCenter(i)));
                localCSPlanesPlus.Add(new Plane(offsetPlus.Faces.GetFaceCenter(i), localCSPlanes[i].XAxis, localCSPlanes[i].YAxis));
            }
          
            //This for-cycle creates a index-consistent list of minus-offset mesh face center points and local coordinate system mesh planes.
            int nFcsMn = offsetMinus.Faces.Count;
            int nEdgMn = offsetMinus.TopologyEdges.Count;

            for (int i = 0; i <= nFcsMn - 1; i++)
            {
                meshFaceCenterMinus.Add(new Point3d(offsetMinus.Faces.GetFaceCenter(i)));
                localCSPlanesMinus.Add(new Plane(offsetMinus.Faces.GetFaceCenter(i), localCSPlanes[i].XAxis, localCSPlanes[i].YAxis));               
            }

            for (int i = 0; i <= nEdg - 1; i++)
            {

                Line lineRecPlus = offsetPlus.TopologyEdges.EdgeLine(i);
                edgeMeshPlusLine.Add(lineRecPlus);

                Point3d recPointA = lineRecPlus.From;
                recMesh.Vertices.Add(recPointA);

                Point3d recPointB = lineRecPlus.To;
                recMesh.Vertices.Add(recPointB);

                Line lineRecMinus = offsetMinus.TopologyEdges.EdgeLine(i);
                edgeMeshMinusLine.Add(lineRecMinus);

                Point3d recPointC = lineRecMinus.To;
                recMesh.Vertices.Add(recPointC);

                Point3d recPointD = lineRecMinus.From;
                recMesh.Vertices.Add(recPointD);

                recMesh.Faces.AddFace(0 + 4 * i, 1 + 4 * i, 2 + 4 * i, 3 + 4 * i);
           

NOTE: I know how to create a solid from a single mesh surface, but this is not what I want now, because I have to sort (for further purpose) the solid mesh in top, bottom and side faces.

Thanks a lot for your help!

cheers,

matteo