How does a queue interact with a foreach loop

Question

I was really suprised that this question doesn't really have an answer. For example I have a foreach loop iterating through the queue(I am using the .Net versions) what exactly happens to the queue in the foreach? Does it simply iterates like a standard enumerator? Or does it use the Dequeue() functionality.

For clarity:

Queue<int> q = new Queue<int>();
foreach(int i in q)
{
    // what happens in this loop?
}

Answer 1

Does it simply iterates like a standard enumerator? Or does it use the Dequeue()

Instead of iterating the queue, it looks up elements by index and bucket in its internal array, using the Queue<T>.GetElement method. You can see this in the implementation of the Enumerator class returned by Queue<T>.GetEnumerator():

public bool MoveNext() 
{
    if (_version != _q._version)
        ThrowHelper.ThrowInvalidOperationException(
                                    ExceptionResource.InvalidOperation_EnumFailedVersion);

    if (_index == -2)
        return false;

    _index++;

    if (_index == _q._size) 
    {
        _index = -2;
        _currentElement = default(T);
        return false;
    }

    _currentElement = _q.GetElement(_index);
    return true;
}

Where GetElement is simply:

internal T GetElement(int i)
{
    return _array[(_head + i) % _array.Length];
}