Проблема с IEnumerator

есть своя реализация dictionary:

public class MyDictionary<TKey, TValue> : IEnumerable<KeyValuePair<TKey,TValue>>
{
    private int _count;
    private Node<TKey, TValue>[] _storage;
    private readonly int _currentSize;
    private const int DefaultSize = 100;
    public MyDictionary(int size)
    {
        _currentSize = size;
        _storage = new Node<TKey, TValue>[size];
    }
    public MyDictionary()
    {
        _currentSize = DefaultSize;
        _storage = new Node<TKey, TValue>[DefaultSize];
    }
    public int Count()
    {
        return _count;
    }
    public void Add(TKey key, TValue value)
    {
        if (ContainsKey(key))
        {
            throw new ArgumentException($"Dictionary already contain this key: {key}");
        }
        var pos = GetPosition(key);
        Add(pos, key, value);
        _count++;
    }
    public bool ContainsKey(TKey key)
    {
        foreach (var node in _storage)
        {
            if ( node != null && node.Next != null)
            {
                var tmp = node;
                while (tmp != null)
                {
                    if (tmp.Key.Equals(key))
                    {
                        return true;
                    }
                    tmp = tmp.Next;
                }
            }
            if (node != null && node.Key.Equals(key))
            {
                return true;
            }
        }
        return false;
    }
    public bool ContainsValue(TValue value)
    {
        foreach (var node in _storage)
        {
            if (node?.Next != null)
            {
                var tmp = node;

                while (tmp != null)
                {
                    if (tmp.Value.Equals(value))
                    {
                        return true;
                    }
                    tmp = tmp.Next;
                }
            }
            if (node != null && node.Value.Equals(value))
            {
                return true;
            }
        }
        return false;
    }
    public void Remove(TKey key)
    {
        if (!ContainsKey(key))
        {
            throw new ArgumentException($"Dictionary not contain the value with key: {key}");
        }
        var pos = GetPosition(key);
        if (_storage[pos].Next == null)
        {
            _storage[pos] = null;
            _count--;
            return;
        }
        var tmp = _storage[pos];
        _storage[pos] = null;
        while (tmp != null)
        {
            if (!tmp.Key.Equals(key))
            {
                Add(pos, tmp.Key, tmp.Value);
            }
            tmp = tmp.Next;
        }
        _count--;
    }
    public void Clear()
    {
        _storage = new Node<TKey, TValue>[_currentSize];
        _count = 0;
    }
    private void Add(int pos, TKey key, TValue value)
    {
        if (_storage[pos] != null)
        {
            var tmp = _storage[pos];
            while (tmp.Next != null)
            {
                tmp = tmp.Next;
            }
            tmp.Next = new Node<TKey, TValue>() { Key = key, Value = value };
        }
        else
        {
            _storage[pos] = new Node<TKey, TValue>() { Key = key, Value = value };
        }
    }
    private int GetPosition(TKey key)
    {
        return Math.Abs(key.GetHashCode() % _currentSize);
    }
    public IEnumerator<KeyValuePair<TKey, TValue>> Enumerator()
    {
        foreach (var node in _storage)
        {
            if (node == null) continue;
            if (node.Next != null)
            {
                var current = node;
                while (current != null)
                {
                    yield return new KeyValuePair<TKey, TValue>(current.Key, current.Value); 
                    current = current.Next;
                }
            }
            else
            {
                yield return new KeyValuePair<TKey, TValue>(node.Key, node.Value);
            }
        }
    }
    IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator()
    {
        return Enumerator();
    }
    public IEnumerator GetEnumerator()
    {
        return Enumerator();
    }
}
internal class Node<TKey, TValue>
{
    public TValue Value { get; set; }
    public TKey Key { get; set; }
    public Node<TKey, TValue> Next;
}

и при проходе по нему с помощью foreach он возвращает object вместо KeyValuePair подскажите в чем проблема