Question

What exactly is it, or was it, as is a interop, used for?

Here, this is the method where I use it:

    public void SaveAttachmentMime(String fileName, CDO.Message message)
    {
        ADODB.Stream stream = message.BodyPart.GetStream();

        String messageString = stream.ReadText(stream.Size);

        StreamWriter outputStream = new StreamWriter(fileName);

        outputStream.Write(messageString);
        outputStream.Flush();
        outputStream.Close();
    }

Answer 1

The ADODB.Stream object was used to read files and other streams. What it does is part of what the StreamReader, StreamWriter, FileStream and Stream does in the .NET framework.

For what the code in that method uses it for, in .NET you would use a StreamReader to read from a Stream.

Note that the code in the method only works properly if the stream contains non-Unicode data, as it uses the size in bytes to determine how many characters to read. With a Unicode encoding some characters may be encoded as several bytes, so the stream would run into the end of the stream before it could read the number of characters specified.