How do I concatenate two System.Io.Stream instances into one?

Question

Let\'s imagine I want to stream three files to a user all in a row, but instead of him handing me a Stream object to push bytes down, I have to hand him a

Answer 1

Untested, but something like:

class StreamEnumerator : Stream
{
    private long position;
    bool closeStreams;
    IEnumerator iterator;
    Stream current;
    private void EndOfStream() {
        if (closeStreams && current != null)
        {
            current.Close();
            current.Dispose();
        }
        current = null;
    }
    private Stream Current
    {
        get {
            if(current != null) return current;
            if (iterator == null) throw new ObjectDisposedException(GetType().Name);
            if (iterator.MoveNext()) {
                current = iterator.Current;
            }
            return current;
        }
    }
    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            EndOfStream();
            iterator.Dispose();
            iterator = null;
            current = null;
        }
        base.Dispose(disposing);
    }
    public StreamEnumerator(IEnumerable source, bool closeStreams)
    {
        if (source == null) throw new ArgumentNullException("source");
        iterator = source.GetEnumerator();
        this.closeStreams = closeStreams;
    }
    public override bool CanRead { get { return true; } }
    public override bool CanWrite { get { return false; } }
    public override void Write(byte[] buffer, int offset, int count)
    {
        throw new NotSupportedException();
    }
    public override void WriteByte(byte value)
    {
        throw new NotSupportedException();
    }
    public override bool CanSeek { get { return false; } }
    public override bool CanTimeout { 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()
    { /* nothing to do */ }
    public override long Length
    {
        get { throw new NotSupportedException(); }
    }
    public override long Position
    {
        get { return position; }
        set { if (value != this.position) throw new NotSupportedException(); }
    }
    public override int Read(byte[] buffer, int offset, int count)
    {
        int result = 0;
        while (count > 0)
        {
            Stream stream = Current;
            if (stream == null) break;
            int thisCount = stream.Read(buffer, offset, count);
            result += thisCount;
            count -= thisCount;
            offset += thisCount;
            if (thisCount == 0) EndOfStream();
        }
        position += result;
        return result;
    }
}