Question

Suppose you have a library that provides a method that accepts an object that needs to be cleaned up. E.g. by calling its Close or Dispose method. Who should be responsible? The caller or callee? Ofcourse you can choose either way as long as you document this properly. But is there consensus or best practice about this?

Here is an example:

// public method of library
public class MyObject
{
   public void Read(System.IO.Stream stream)
   {
      ...
   }
   ...
}

If the caller would be responsible, the client code should look like this:

using (FileStream file = new FileStream(...))
{
   MyObject myObject = new MyObject();
   myObject.Read(file);
}

Answer 1

I would say the normal “ownership” is for whoever creates the resource to start with – so the caller of your method. Aside from anything else, who’s to say that the caller wants to dispose of the stream after reading? Perhaps they want to rewind it and pass it to something else.

I generally get nervous of disposing of anything I haven’t explicitly created. There are exceptions to this of course – the Bitmap(Stream) constructor effectively takes ownership of the stream, and assumes that you’ll dispose of the bitmap which will in turn dispose of the stream… but I’d say that’s the exception rather than the rule.