GetNextPosition in maze (2d array)

I'm trying to implement GetNextPosition in maze (2d array).

Here is sample code with logic I'm trying to implement.

The problem is, I don't know how to return the next position. I know it should be a boolean, or at least that's how I wrote the main function. Maybe my approach is completely wrong and I'm making things harder then they should be.

public class DwarfLeft : DwarfBase
{
    public override ConsoleColor Color => ConsoleColor.Yellow;

    private int _angle;

    public DwarfLeft(Maze m) : base(m.StartX, m.StartY)
    {
        //Entry validation
        _angle = m.StartAngle;
    }

    public override bool GetNextPosition(out int nx, out int ny)
    {
        // "return" new position based on _angle and X,Y
    }

    public override void NextPositionUnreachable()
    {
        // Didn't moved
        OldX = X;
        OldY = Y;

        _angle += 90;
        if (_angle > 360) _angle = _angle - 360;
    }
}

What i'm trying to do here is getting the next position where the dwarf could move on

    class Program
    {
        static void Main(string[] args)
        {
            var src = "D:\\1\\maze.dat";
            var maze = new MazeLoader().LoadMaze(src);

            var dwarfs = new List<DwarfBase>();

            MazePresenter.Render(maze);

            dwarfs.Add(new DwarfLeft(maze));

            while (dwarfs.Count > 0)
            {
                #region movement

                for (var i = 0; i < dwarfs.Count; i++)
                {
                    int nx, ny;
                    if (!dwarfs[i].GetNextPosition(out nx, out ny)) continue;

                    // check for BlockType
                    var bc = maze.GetBlockType(nx, ny);
                    switch (bc)
                    {
                        // if pos. == finish || "space" - go there
                        case eBlockType.Space:
                        case eBlockType.Finish: dwarfs[i].MoveToPosition(nx, ny); continue;
                        default:
                            // if pos. unreachable - rotate x axis and repeat procedure
                            dwarfs[i].NextPositionUnreachable();
                            continue;
                    }
                }

                #endregion
            }
        }
    }
}

The maze is rectangular, made of '#' for wall, 'S' for start, 'F' for finish and ' ' for position where dwarf can move.

Thanks in advance for any help, I really appreciate it and happy rest of Easter :)