how to reverse iterate over Queue?

Question

foreach loop iterates over Queue starting from the oldest item and ending with newest. What if I need to start with newest and end with oldest (probably interrupting at some point as in most cases I just need to iterate over several newest items)?

i'm looking for straighforward and efficient solution. without recreating new objects.

Answer 1

You could use Linq's Reverse() function:

Queue myQueue;

foreach (var item in myQueue.Reverse())
{
    // do things
}

Answer 2

Both Reverse() and ToArray() have bad performance. If possible, change Queue<T> to LinkedList<T>.

LinkedList works like a deque (https://en.wikipedia.org/wiki/Double-ended_queue).

More details: https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.linkedlist-1