C# A Small HashSet for Quick Loading & Lookups

SmallHashSet.cs

public class SmallHashSet<T>
    {
        private int[]  _hashBuckets;
        private uint   _hashCode;
        public  Data[] Datas;
        public SmallHashSet() : this(4096)
        {
        }
        public SmallHashSet(int size)
        {
            Initialize(size);
        }
        public int  Count   {get; private set;}
        public bool IsDirty => Count != _hashBuckets.Length;
        public bool Add(T item)
        {
            return Insert(item);
        }
        public bool Contains(T item)
        {
            return FindItem(item) != -1;
        }
        public void Clean()
        {
            if(Count == 0) return;
            var newhashebuckets = new int[Count];
            var newdatas        = new Data[Count];
            Array.Copy(Datas, newdatas, Count);
            newhashebuckets.Fill(-1);
            for(var i = 0; i < Count; i++)
            {
                var pos     = newdatas[i].hashCode % Count;
                var prevpos = newhashebuckets[pos];
                newhashebuckets[pos] = i;
                if(prevpos != -1)
                    newdatas[i].next = prevpos;
            }
            _hashBuckets = newhashebuckets;
            Datas        = newdatas;
        }
        private bool Insert(T item)
        {
            if(FindItem(item) != -1)
                return false;
            try
            {
                if(Count >= Datas.Length)
                    Resize();
            }
            catch(Exception e)
            {
                throw new Exception($"Error resizing hash bucket list {e.Message}");
            }
            var hashPos = _hashCode % (uint) _hashBuckets.Length;
            var nextPos = _hashBuckets[hashPos];
            _hashBuckets[hashPos] = Count;
            Datas[Count].next     = nextPos;
            Datas[Count].value    = item;
            Datas[Count].hashCode = _hashCode;
            Count++;
            return true;
        }
        public int FindItem(T item)
        {
            _hashCode = (uint) item.GetHashCode() & int.MaxValue;
            for(var position = _hashBuckets[_hashCode % _hashBuckets.Length]; position >= 0; position = Datas[position].next)
                if(Datas[position].hashCode == _hashCode && EqualityComparer<T>.Default.Equals(Datas[position].value, item))
                    return position;
            return-1;
        }
        private void Resize(int newsize = 0)
        {
            if(newsize == 0)
                newsize = (int) (_hashBuckets.Length * 2.5f);
            var newhashebuckets = new int[newsize];
            var newdatas        = new Data[newsize];
            Array.Copy(Datas, newdatas, Count);
            newhashebuckets.Fill(-1);
            for(var i = 0; i < Count; i++)
            {
                var pos     = newdatas[i].hashCode % newsize;
                var prevpos = newhashebuckets[pos];
                newhashebuckets[pos] = i;
                if(prevpos != -1)
                    newdatas[i].next = prevpos;
            }
            _hashBuckets = newhashebuckets;
            Datas        = newdatas;
        }
        private void Initialize(int size)
        {
            _hashBuckets = new int[size];
            Datas        = new Data[size];
            Count        = 0;
            _hashBuckets.Fill(-1);
        }
        public struct Data
        {
            public uint hashCode;
            public int  next;
            public T    value;
        }
    }