https://www.reddit.com/r/csharp/comments/sgt997/i_raise_your_cursed_foreach_with_this_cursed/huzl9nm/

CursedBuffer.cs

namespace Demo 
{
    public class CursedBuffer
    {
        private readonly object[] data;
        private readonly Pointer pointer;

        public CursedBuffer(int size)
        {
            data = new object[size];
            pointer = new Pointer(size);
        }

        private sealed class Pointer
        {
            private readonly int limit;

            public Pointer(int limit) => this.limit = limit;

            private int _pointer = 0;

            public void Set(int value) => _pointer = value;

            public int Advance()
            {
                var value = _pointer;
                _pointer++;
                return value;
            }

            public bool AtEnd() => _pointer >= limit;
        }

        public object _
        {
            get
            {
                if (pointer.AtEnd())
                {
                    return null;
                }
                return data[pointer.Advance()];
            }
            set
            {
                if (value is int intValue)
                {
                    pointer.Set(intValue);
                    return;
                }
                if (pointer.AtEnd())
                {
                    return;
                }
                data[pointer.Advance()] = value;
            }
        }

        public static implicit operator bool(CursedBuffer buffer)
        {
            return buffer.pointer.AtEnd() == false;
        }

        internal sealed class CursedBufferTest : CursedBuffer
        {
            public CursedBufferTest() : base(13)
            {
                _ = 'H'; _ = 'e'; _ = 'l'; _ = 'l'; _ = 'o'; _ = ','; _ = ' ';
                _ = 'w'; _ = 'o'; _ = 'r'; _ = 'l'; _ = 'd'; _ = '!'; _ = 0;

                var sb = new StringBuilder();

                for (var value = _; this; value = _) sb.Append(value);

                var result = sb.ToString();

                Debug.WriteLine(result); /* Output: Hello, world! */
            }
        }
    }
 }