Question

I’m attempting to mock some file operations. In the “real” object I have:

StreamWriter createFile( string name )
{
  return new StreamWriter( Path.Combine( _outFolder, name ), false, Encoding.UTF8 ) );
}

In the mock object I’d like to have:

StreamWriter createFile( string name )
{
  var ms = new MemoryStream();
  _files.Add( Path.Combine( _outFolder, name ), ms );
  return new StreamWriter( ms, Encoding.UTF8 ) );
}

where _files is a dictionary to store created files for later inspection.

However, when the consumer closes the StreamWriter, it also disposes the MeamoryStream… 🙁

Any thoughts on how to pursue this?

Answer 1

If you subclass the MemoryStream, this will work but you have to call ManualDispose method to close the underlying stream.
I´m not sure but I think this object will be garbage-collected when it goes out of scope.

public sealed class ManualMemoryStream : MemoryStream
{
    protected override void Dispose(bool disposing)
    {
    }
    public void ManualDispose()
    {
        base.Dispose(true);
    }
}

Edit:
This is an alternative if you want the MemoryStream to be flushed and ready to be read from top.

public sealed class ManualMemoryStream : MemoryStream
{
    protected override void Dispose(bool disposing)
    {
        Flush();
        Seek(0, SeekOrigin.Begin);
    }
    public void ManualDispose()
    {
        base.Dispose(true);
    }
}