Open IDataReader result column as stream using IDataReader.GetBytes.

DataReaderStream.cs

using System;
using System.Data;
using System.IO;

namespace Company.Product
{
    internal class DataReaderStream : Stream
    {
        private long _position = 0L;
        private readonly IDataReader _reader;
        private readonly int _index;

        public DataReaderStream(IDataReader reader, int index)
        {
            _reader = reader;
            _index = index;
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            long read = _reader.GetBytes(_index, _position, buffer, offset, count);
            _position += read;
            return (int)read;
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            throw new NotSupportedException();
        }

        public override long Position
        {
            get { return _position; }
            set { throw new NotSupportedException(); }
        }

        public override long Length
        {
            get { throw new NotSupportedException(); }
        }

        public override bool CanWrite
        {
            get { return false; }
        }

        public override bool CanRead
        {
            get { return true; }
        }

        public override bool CanSeek
        {
            get { return false; }
        }

        public override void SetLength(long value)
        {
            throw new NotSupportedException();
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            throw new NotSupportedException();
        }

        public override void Flush()
        {
            throw new NotSupportedException();
        }
    }
}