if you have a polyline layer then to highlight a point you need to add a point layer. There are tons of examples here where you can get started https://dotspatial.codeplex.com/documentation
I have a map with a polygon layer where the categories change based on what the user has selected. Say they choose Car Type A then I clear the categories and create new ones that are appropriate for that choice. if they choose Car Type B then again I clear categories and rebuild them for the appropriate type.
I have a map with a polygon layer where the categories change based on what the user has selected. Say they choose Car Type A then I clear the categories and create new ones that are appropriate for that choice. if they choose Car Type B then again I clear categories and rebuild them for the appropriate type.