class MyStream : Stream
{
    public MyStream()
    {
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        return 0;
    }


    public override void Write(byte[] buffer, int offset, int count)
    {
        MyFunction(buffer); // <-- My function here
    }
    public override void Close()
    {

    }

    public override long Length
    {
        get { return 0; }
    }

    // Abstract methods below //
    public override long Seek(long offset, SeekOrigin origin) { return 0; }

    public override void SetLength(long value) { }
    public override void Flush() { }

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

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

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

    public override long Position
    {
        get
        {
            return 0;
        }
        set
        {
            return;
        }
    }
}