Colliding a List of Shapes Against Itself

Storing shapes (or Entities which have collision shapes) in a list is very common. You can collide all objects in a list all other objects using doubly-nested for loops:

// Assuming myList is a valid List of shapes
for(int firstIndex = 0; firstIndex < myList.Count; firstIndex++)
{
   for(int secondIndex = 0; secondIndex < myList.Count; secondIndex++)
   {
      // Make sure a shape doesn't collide against itself
      if(firstIndex != secondIndex && 
         myList[firstIndex].CollideAgainst(myList[secondIndex]))
      {
         // do whatever you need to do to respond to collisions here
      }
   }
}