Question

I have List<QueueItem> QueueItemList list of objects. I am filtering the objects list by object property Status and assign filtered list to processingList. If I will change object Status property in the QueueItemList list does it will be changed in processingList too?

        public List<QueueItem> GetItems()
        {
            lock (Locker)
            {
                return QueueItemList.ToList();
            }
        }

var processingList = GetItems.Where(p => p.Status== QueueItemStatus.Processing).ToList();

Answer 1

If I will change object Status property in the QueueItemList list
does it will be changed in processingList too?

Yes, it will, unless QueueItem is a value type (struct). If it is a class then it is a reference type, meaning that both processingList and QueueItemList are pointing to the exact same memory location for their elements. Those variables are just pointers.