### xna-4.0

#### XNA choosing a subgroup of Game.Components

```G'day All,
My little game has 5 bouncing balls and 1 player. Initially I wrote the code for the bouncing balls first and each ball has a collision detection method:
foreach (Bouncer bouncer in Game.Components) //For each bouncer component in the game...
{
if (bouncer != this)// Don't collide with myself
{
if (bouncer.collisionRectangle.Intersects(this.collisionRectangle))
{
// How far apart of the positions of the top right hand corners of the sprites when they hit?
int deltaX = Math.Abs((int)this.position.X - (int)bouncer.position.X);
int deltaY = Math.Abs((int)this.position.Y - (int)bouncer.position.Y);
// This is the width and height of a sprite so when two sprites touch this is how far the corners are from each other.
int targetWidth = 80;
int targetHeight = 80;
// The following determins the type of collision (vert hit vs horiz hit)
// Because the app is driven by a game based timer the actual amount of sprite overlap when the collision detection occurs is variable.
// This bit of simple logic has a 10 pixel tollerance for a hit.
// If target - delta is > 10 it will be interpreted as overlap in the non-colliding axis.
// If both if statements are triggered it is interpreted as a corner collision resulting in both sprites rebounding back along the original paths.
if (targetWidth - deltaX < 10) // The hit is a side on hit.
{
this.velocity.X *= -1;
}
if (targetHeight - deltaY < 10) // The hit is a vertical hit
{
this.velocity.Y *= -1;
}
this.numberOfCollisions = this.numberOfCollisions + 1;
}
}
}
base.Update(gameTime);
}
Then I added my player component and the wheels fell off. The app compiles OK but when I run it I get an InvalidCastException and the message:
Unable to cast object of type 'Bounce2.Player' to type 'Bounce2.Bouncer'.
I don't want to include the player object in this collision detector.
Is there a way I can enumerate my way through the Bouncer objects and exclude any other objects?
Thanks,
Andrew.
```
```You can use this:
foreach (Bouncer bouncer in Game.Components.OfType<Bouncer>())
Note that you can store the Bouncer instances in other list too.```

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