Vector3d operators

        public static Vector3d operator +(Vector3d left, Vector3d right)
        {
            left.X += right.X;
            left.Y += right.Y;
            left.Z += right.Z;
            return left;
        }

        public static Vector3d operator +(Vector3d left, Vector3d right)
        {
            return new Vector3d(left.X + right.X, left.Y + right.Y, left.Z + right.Z);
        }

    Vector3d first = new Vector3d(1, 1, 1);
    Vector3d second = new Vector3d(2, 2, 2);
    Vector3d result = first + second;