PhiAI is a C# library downloadable as a NuGet package that can be used to implement game AI. It is currently in alpha and features the Monte Carlo Tree Search Algorithm (MCTS). MCTS is a heuristic algorithm that is great for use in perfect information, zero-sum games like chess, go, tic-tac-toe, etc.
PhiAI began shortly after my obsessive studying of Deepmind's AlphaGo and AlphaZero research papers. Under the hood, both algorithms use a Monte Carlo Tree Search (MCTS). MCTS is fairly domain agnostic, so I wanted to make a generic implementation that people could use to create AI in whatever domain they wanted. Future releases will feature many more algorithms.