Adding Objects More Than To ArrayList

I'm developing a simple shooter game in XNA. I'm adding the copy of the object to an array list whenever it hits an hostile. The problem is, the object is added 2 times.

Here is the code:

--> Player fires spheres.

--> s is fired sphere

--> sp is copy of s

--> a sphere is drawn iff it's active

if(s.isCollided)
{
     s.isCollided = false;
     Sphere sp = new Sphere(s.texture, new Vector2(s.dest_rectangle.X,s.dest_rectangle.Y), s.speed);
     s.dest_rectangle = new Rectangle((int)s.position.X, (int)s.position.Y, s.texture.Width, s.texture.Height);
     sp.isActive = tru开发者_Python百科e;
     sp.isCollided = false;
     collidedSpheres.Add(sp);
 }

It's possible that s is colliding with your hostile during two "frames".

You could try adding this line to the end of your function: spheres.Remove(s);.

Do the duplicate spheres have the same position?