A C# implementation of a HPA* algorithm, based on the paper "Near-Optimal Hierarchical Pathfinding (HPA*)" (https://webdocs.cs.ualberta.ca/~jonathan/publications/ai_publications/jogd.pdf), from the original C++ code that can be found in https://webdocs.cs.ualberta.ca/~games/pathfind/hpa.tgz. The code also is being refactored a bit to enhance integration with grid-based games.
You can find more interesting articles related to AI at https://webdocs.cs.ualberta.ca/~games/