Declaring types

ray.cs

class Ray
   {
      private readonly Vector3D position;
      private readonly Vector3D direction;
      public Ray(Vector3D position, Vector3D direction)
      {
         this.position = position;
         this.direction = direction;
      }

      public Vector3D Position { get { return position; } }
      public Vector3D Direction { get { return direction; } }
   }