Question

I am building a space invader game and I use this linq method to see if the invaders were hit by the player:

foreach (var playerShot in playerShots)
{
    if (isWeapon)
    {
        AliensHit = from invader2 in invaders
                    where invader2.Area.Contains(playerShot.Area)
                    select invader2;
    }
}

later I have an algorithm that removes the shot and the invader, but that doesn’t matter as
the contains method doesnt work.
I fire a shot which is a bitmap, and it passes through the invader..(its Area property changes correctly, I checked with the debugger, and so the invaders Area changes: they both move.).
Then I checked with a smaller rectangle shot, if the rectangle shot is in the invaders Area and it worked. Both were removed.

AliensHit = from invader in invaders
            where invader.Area.Contains(playerShot.Location)
            select invader;

Why when I put an area to check the method doesn’t work, I checked for 3 hours with the debugger and found nothing wrong. 🙁

Answer 1

The problem sounds like the use of Contains. This will return true if and only if the shot rectangle is wholly within the invader rectangle. With a smaller playerShot this will happen more often.

You probably want to use .Intersect(playerShot.Area) instead – this will return true if the two areas overlap at all.

Edit: As noted by the OP, .IntersectsWith(playerShot.Area) is the method I meant!