High-Performance Stream Processing in C#

Reusable Stream

You need to install Microsoft.IO.RecyclableMemoryStream.

    internal class StreamHandler
    {
        // Stream pool
        private static readonly RecyclableMemoryStreamManager Manager = new();

        private readonly RecyclableMemoryStream _stream;
        private volatile bool _disposed;
        
        public Stream Stream => _stream;
        
        public ResponseHandler()
        {
            _stream = (Manager.GetStream() as RecyclableMemoryStream)!;
        }
        
        public ReadOnlySequence<byte> GetReadOnlySequence() => _stream.GetReadOnlySequence();

        public void Dispose()
        {
            if (_disposed) return;
            _disposed = true;
            _stream.Dispose();
            GC.SuppressFinalize(this);
        }

        public ValueTask DisposeAsync()
        {
            if (_disposed) return ValueTask.CompletedTask;
            _disposed = true;
            return _stream.DisposeAsync();
        }

        public ValueTask InvokeAsync()
        {
            return ValueTask.CompletedTask;
        }

        ~ResponseHandler()
        {
            Dispose();
        }
    }

PipeReader and PipeWriter

You need to include System.IO.Pipelines.
It provides a more convenient way to work with byte arrays.

        Stream stream = .... .... 
         
        ReadOnlySequence<byte> sequence;
        PipeReader pipeReader = PipeReader.Create(stream, new StreamPipeReaderOptions(bufferSize: Environment.SystemPageSize));
        var result = await pipeReader.ReadAsync();
        sequence = result.Buffer;
        
        var ex = new Exception();
        if (pipeReader != null)
        {
            await pipeReader.CompleteAsync(ex);
        }