The API for Civil 3D, as far as I know, doesn't have way to add pipes or structures to a profile view. There is a possible workaround using AutoCAD's SendCommand. The code would look something like this:
ThisDrawing.SendCommand ("AddNetworkPartsToProf " & "3741.54989837,3396.84999773 " & " " & _
The first ZoomExtents is to refresh model space because if the graphics aren't current AutoCAD won't recognize the newly created pipe/structure or profile view. The next part sends the commands to the command line. The AddNetworkPartsToProf is the command to in Civil 3D to add pipe/structures to a profile view. The next part is the coordinate location of where a pipe/structure is located in the drawing and the last part is the point in the drawing where a profile view may be selected. The last ZoomExtents is just for show. The & symbol joins text strings together.