I am translating a solution to the Mars Rover problem written in Java. I am not sure how to deal with the Direction enum class found here.
I don't think I can do it like that in C#, therefore I would like to ask if anyone could suggest how to do this.
I was thinking of making an IDirection interface and a class for each Direction that inherits from that interface.
You could use a struct for this purpose, with a selected set of global singletons representing standard directions. I suggest a struct since your Direction object has value semantics:
public struct Direction : IEquatable<Direction> { short xstep; short ystep; public static Direction N { get { return new Direction(0, 1); } } public static Direction E { get { return new Direction(1, 0); } } public static Direction S { get { return new Direction(0, -1); } } public static Direction W { get { return new Direction(-1, 0); } } public static IEnumerable<Direction> Directions { get { yield return N; yield return E; yield return S; yield return W; } } Direction(int x, int y) { this.xstep = checked((short)x); this.ystep = checked((short)y); } public int XStep { get { return xstep; } } public int YStep { get { return ystep; } } public Direction Left { get { return new Direction(-YStep, XStep); } } public Direction Right { get { return new Direction(YStep, -XStep); } } public override bool Equals(object obj) { if (obj is Direction) { var other = (Direction)obj; return xstep == other.XStep && ystep == other.YStep; } return false; } public override int GetHashCode() { return (XStep.GetHashCode() | (YStep << 16).GetHashCode()); } #region IEquatable<Direction> Members public bool Equals(Direction other) { return this.xstep == other.xstep && this.ystep == other.ystep; } #endregion public static Direction operator -(Direction direction) { return new Direction(-direction.XStep, -direction.YStep); } public static bool operator ==(Direction first, Direction second) { return first.Equals(second); } public static bool operator !=(Direction first, Direction second) { return !(first == second); } public override string ToString() { if (this == Direction.N) return "N"; if (this == Direction.E) return "E"; if (this == Direction.S) return "S"; if (this == Direction.W) return "W"; return string.Format("({0},{1}}", XStep.ToString(NumberFormatInfo.InvariantInfo), YStep.ToString(NumberFormatInfo.InvariantInfo)); } } The public static bool operator ==(Direction first, Direction second) allows directions to be compared simply using the == operator. This also requires overriding Equals and GetHashCode().
Debug.Assert(Direction.N.Left == Direction.W && Direction.N.Right == Direction.E);.Direction? All of the solutions presented here (immutable structs and classes with private constructors and a fixed set of global singletons) present challenges for serialization.In C# enums are simple wrapper types over a finite set of primitive types, and sadly extension methods are the only way to extend them.
In Java, they're classes which you can extend with their own methods.
All you need to do is emulate that behavior. A possible approach could be:
public sealed class Direction { public static readonly Direction N = new Direction(0, 1); public static readonly Direction S = new Direction(0, -1); public static readonly Direction E = new Direction(1, 0); public static readonly Direction W = new Direction(-1, 0); static Direction() { N.Left = W; N.Right = E; S.Left = E; S.Right = W; E.Left = N; E.Right = S; W.Left = S; W.Right = N; } private Direction(int stepSizeOnXAxis, int stepSizeOnYAxis) { StepSizeForXAxis = stepSizeOnXAxis; StepSizeForYAxis = stepSizeOnYAxis; } public Direction Right { get; private set; } public Direction Left { get; private set; } public int StepSizeForXAxis { get; } public int StepSizeForYAxis { get; } } 
Direction.N.Left == Direction.W seems redundant.Despite the fact that java seems to have this feature which C# doesn't, the reality is (as always) that C# is a much more modern language, and it requires much less code to produce the same results.
Your 72 lines of java code can be translated into these 35 lines of C#:
public class Direction { public static readonly Direction N = new Direction(0, 1); public static readonly Direction S = new Direction(0, -1); public static readonly Direction E = new Direction(1, 0); public static readonly Direction W = new Direction(-1, 0); private Direction(int stepSizeX, int stepSizeY) { this.StepSizeForXAxis = stepSizeX; this.StepSizeForYAxis = stepSizeY; } static Direction() { N.Left = W; N.Right = E; S.Left = E; S.Right = W; E.Left = N; E.Right = S; W.Left = S; W.Right = N; } public Direction Left { get; private set; } public Direction Right { get; private set; } public int StepSizeForXAxis { get; private set; } public int StepSizeForYAxis { get; private set; } } This results in a class that can only be instantiated by itself (because of the private constructor), and has members that you can use in the same way you would use a C# enum, with the advantage of the additional properties:
var south = Direction.S; var east = south.Left; Console.WriteLine(east == south); // True Console.WriteLine(south.StepSizeForXAxis); //0 Console.WriteLine(south.StepSizeForYAxis); //-1 java can be hardly compared to C# anymore, let alone claim any advantage over it, at least at the language level.
N, the variables W and E are still null. Oh, and there's no such thing as C# 7 yet :)
Directionwith a protected constructor. Then create subclasses inside the Direction for each direction, and create static fields in the Direction class for each direction. Alternatively, use a library such as this.(x, y)90 degrees counterclockwise, which results mathematically in in(-y, x). Similarly "right" results in(y, -x).