Question

I have a loop that is supposed to detect and remove any objects in a list that intersect with an object being placed. The code is as follows:

for (int i = 0; i < levelObjects.Count(); i++)
{
    if (levelObjects[i].BoundingBox.Intersects(mouseBlock.BoundingBox))
    {
        levelObjects.RemoveAt(i);
    }
}

When encountering a situation where there are multiple collisions, it sometimes does not detect the collision. The intersection function is working fine. What is it about my loop that’s causing this?

Answer 1

Since you’re removing from the loop, you end up skipping elements. A better option would be to loop backwards:

for (int i=levelObjects.Count() - 1; i >= 0; --i)
{
  // ...

This prevents the “skipped” object that you’re missing now, since when you remove, and the indices shift downwards, you’re only shifting objects whom you’ve already tested.