The Weird and The Wonderful

Fandango90 wrote:

A true Primary Key is one created based on data "snippets" off other columns in the table.

Fandango90 wrote:

the same mistakes. Primary key every table with an auto-fill ID column

Fandango90 wrote:

Yes, you have a primary key, congratulations! But what's the point if you don't have a reference to the ID from another table?

Fandango90 wrote:

Did someone forget that the ID Primary Key column is a machine necessity, if at all? Like who care my next record starts with ID 2001!?

Fandango90 wrote:

A true Primary Key is one created based on data "snippets" off other columns in the table

raddevus wrote:

I assumed, but wasn't sure.
This code gives a good definitive answer.

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

Richard Deeming wrote:

It also seems that the order of searches has some effect. Try searching for 1st followed by 31st; then try 31st followed by 1s

Kornfeld Eliyahu Peter wrote:

seems to me a very bad practice to use a FIFO/LIFO oriented collection to anything else than push/pop

raddevus wrote:

all I have to do is call .First() on Dictionary when I want the oldest item.

public sealed class UniqueQueue<T> : IEnumerable<T>, IDisposable
{
    private readonly Queue<T> _queue = new Queue<T>();
    private readonly HashSet<T> _set = new HashSet<T>();
    private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim();
    
    public int Count
    {
        get
        {
            bool lockTaken = false;
            try
            {
                lockTaken = _lock.TryEnterReadLock(Timeout.Infinite);
                if (!lockTaken) throw new InvalidOperationException();
                
                return _queue.Count;
            }
            finally
            {
                if (lockTaken)
                {
                    _lock.ExitReadLock();
                }
            }
        }
    }
    
    public void Dispose()
    {
        _lock.Dispose();
    }
    
    public T Dequeue()
    {
        bool lockTaken = false;
        try
        {
            lockTaken = _lock.TryEnterWriteLock(Timeout.Infinite);
            if (!lockTaken) throw new InvalidOperationException();
            
            T oldestItem = _queue.Dequeue();
            _set.Remove(oldestItem);
            return oldestItem;
        }
        finally
        {
            if (lockTaken)
            {
                _lock.ExitWriteLock();
            }
        }
    }
    
    public void AddRange(IEnumerable<T> itemsToAdd)
    {
        if (itemsToAdd == null) throw new ArgumentNullException(nameof(itemsToAdd));
        
        bool lockTaken = false;
        try
        {
            lockTaken = _lock.TryEnterWriteLock(Timeout.Infinite);
            if (!lockTaken) throw new InvalidOperationException();
            
            foreach (T item in itemsToAdd)
            {
                if (_set.Add(item))
                {
                    _queue.Enqueue(item);
                }
            }
        }
        finally
        {
            if (lockTaken)
            {
                _lock.ExitWriteLock();
            }
        }
    }
    
    public UniqueQueueEnumerator GetEnumerator()
    {
        T[] copyOfItems = Array.Empty<T>();
        
        bool lockTaken = false;
        try
        {
            lockTaken = _lock.TryEnterReadLock(Timeout.Infinite);
            if (!lockTaken) throw new InvalidOperationException();
            
            copyOfItems = new T[_queue.Count];
            _queue.CopyTo(copyOfItems, 0);
        }
        finally
        {
            if (lockTaken)
            {
                _lock.ExitReadLock();
            }
        }
        
        return new UniqueQueueEnumerator(copyOfItems);
    }
    
    IEnumerator<T> IEnumerable<T>.GetEnumerator() => GetEnumerator();
    
    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
    
    public struct UniqueQueueEnumerator : IEnumerator<T>
    {
        private readonly T[] _items;
        private int _position;
        
        public UniqueQueueEnumerator(T[] items)
        {
            _items = items;
            _position = -1;
        }
        
        void IDisposable.Dispose()
        {
        }
        
        public void Reset()
        {
            if (_items == null) throw new InvalidOperationException();
            _position = -1;
        }
        
        public bool MoveNext()
        {
            if (_items == null) return false;
            return ++_position < _items.Length;
        }
        
        public T Current
        {
            get
            {
                if (_items == null) throw new InvalidOperationException();
                if (0 > _position || _position >= _items.Length) throw new InvalidOperationException();
                return _items[_position];
            }
        }
        
        object IEnumerator.Current => Current;
    }
}