ReadonlyLockedValue.cs

    internal class ReadonlyLockedValue<T>
    {
        private readonly T _value;

        private readonly object _lockObject;
        private readonly Unlocker _unlocker;

        public ReadonlyLockedValue(T value)
        {
            _value = value;
            _lockObject = new object();
            _unlocker = new Unlocker(this);
        }

        public Unlocker Lock()
        {
            Monitor.Enter(_lockObject);

            return _unlocker;
        }

        private void Unlock()
        {
            Monitor.Exit(_lockObject);
        }

        public class Unlocker
            : IDisposable
        {
            private readonly ReadonlyLockedValue<T> _parent;

            public T Value
            {
                get { return _parent._value; }
            }

            public Unlocker(ReadonlyLockedValue<T> parent)
            {
                _parent = parent;
            }

            public void Dispose()
            {
                _parent.Unlock();
            }
        }
    }