Question

I’m writing an application that creates a “Catalog” of files, which can be attributed with other meta data files such as attachments and thumbnails.

I’m trying to abstract the interface to a catalog to the point where a consumer of a catalog does not need to know about the underlying file system used to store the files. So I’ve created an interface called IFileSystemAdaptor which is shown below.

public interface IFileSystemAdaptor:IDisposable
{
    void WriteFileData(string fileName, Stream data);
    Stream ReadFileData(string filename);
    void DeleteFileData(string filename);
    void ClearAllData();
    void WriteMetaFileData(string filename, string path, Stream data);
    Stream ReadMetaFileData(string filename, string path);
    void DeleteMetaFileData(string filename, string path);
    void ClearMetaFilesData(string filename);
}

Essentially my IFileSystemAdaptor interface exposes a flat list of files, that can also be associated with additional meta data files.

As you can see I’m using references to generic Stream objects to abstract the interface to a file’s data. This way one implementation of a Catalog could return files from a hard disk, while another could return the data from a web server.

Now I’m trying to figure out how to keep my program from leaving streams open. Is there a rule of thumb for what members should close streams? Should the consumer of a stream close it, or should the member that original created the stream be responsible for closing it.

Answer 1

My Rules:

Should the consumer of a stream close it

1. If I return a stream from a method, the consumer is responsible. I’m giving it to you, It’s your responsilibity.

2. If I accept a stream as a parameter in a method, I don’t close it. When exiting the method, I don’t know if the calling method still needs it. It’s your stream, I’m just borrowing it, and I don’t want to mess you up.

3. If I create a stream and pass it to another method, my method closes it (or tries to) when I am done with it. I don’t know what you are going to do with it, but it’s my stream, so I am responsible for it.