Declared enum and IF on its elements

I'm working on Snake game. Although I have a little problem. I created enum with possible directions:

    enum Direction{
    n = 0, // north
    e = 1, // east
    s = 2, // south
    w = 3 // west
};

And then I created a ChangeDirection() function, which basing on previous direction will change it. (For example, if you go to the right/east, you can't switch to left/west):

void ChangeDirection(char key){
    switch (key){
    case 'w':
        if (Direction != 2)
            Direction = 0;
        break;
    case 'd':
        if (Direction != 3)
            Direction = 1;
        break;
    case 's':
        if (Direction != 0)
            Direction = 2;
        break;
    case 'a':
        if (Direction != 1)
            Direction = 3;
        break;
    }

But my ifs clearly don't work; following error occurs:

Expected primary-expression before '!=' token

Anyone could help? How can I rearrange it to work? Why doesn't it work? Thanks!