Question

private Vector2 ResolveCollision(ICollidable moving, ICollidable stationary)
{
    if (moving.Bounds.Intersects(stationary.Bounds))
    {
        if (moving is Player)
        {
            (Player)moving.Color = Color.Red;
        }
    }
    // ...
}

I have a class Player that implements ICollidable. For debugging purposes I’m just trying to pass a bunch of ICollidables to this method and do some special stuff when it’s the player. However when I try to do the cast to Player of the ICollidable I get an error telling me that ICollidable doesn’t have a Color property.

Am I not able to make a cast this way or am I doing something wrong?

Answer 1

I’d suggest using as instead of is:

Player player = moving as Player;
if (player != null)
{
    player.Color = Color.Red;
}

The advantage is that you only do the type check once.

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The specific reason why your code doesn’t work (as mentioned in other answers) is because of operator precedence. The . operator is a primary operator which has a higher precedence than the casting operator which is a unary operator. Your code is interpreted as follows:

(Player)(moving.Color) = Color.Red;

Adding the parentheses as suggested by other answers solves this issue, but changing to use as instead of is makes the issue go away completely.