VCommonCore/VCommon/Collections/ReadonlyHashset.cs

using System.Collections.Generic;

namespace VCommon.Collections
{
    public class ReadOnlyHashSet<T>
    {
        private readonly HashSet<T> _underlying;

        public ReadOnlyHashSet(HashSet<T> underlying) => _underlying = underlying;

        public bool Contains(T value) => _underlying.Contains(value);

        public static implicit operator ReadOnlyHashSet<T>(HashSet<T> instance) => new ReadOnlyHashSet<T>(instance);
    }
}