Few months ago I wrote a 2D platforming game in VB.NET that uses AgateLib game engine.
Check the link here:http://mkasoft.com/index.php/applications/7-2d-game-proj
You will find the stages of game developments with videos and source code. You can go to the last video (no 13) and download the final source code to see how it works or download the installation.
I made only 3 stages due to time and work constraints. You will find that there is a map editor. It is not that easy to use, but it should help you design the stage. Watch the last video (no 13) to see how to use the editor.
hope you find the code useful, and hope some would improve on that project.