public class ChessGame
{
    private readonly Engine _engine;

    public ChessGame()
    {
        var channel = Channel.CreateUnbounded<string>(new UnboundedChannelOptions
        {
            SingleReader = true,
            SingleWriter = true
        });
        _engine = new Engine(channel.Writer);
    }

    public string GetBestMove(string fen)
    {
        _engine.AdjustPosition($"position fen {fen}");
        return _engine.IDDFS(1, 10)
            .BestMove
            .ToEPDString();
    }
}

var fen = "2kr3r/p5p1/2p2P2/5n1p/1p6/1B6/PPP3PP/R1B1Q1K1 b - - 0 20";
var game = new ChessGame();
var best = game.GetBestMove(fen); // Re8