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copied!<p>Daniel is right. I defined a relationships of Import and Export as properties in my mapping classes. I loaded them as ComposablePartCatalog to MEF's container so that MEF can magically fetches corresponding instances on fly. It is within the mapping classes that I have some codes to new instances. Therefore, I have to find a way to let MEF to call back to those mapping classes to dispose the created resources when MEF is out of a process.</p> <p>I like Daniel's suggestion to introduce a class for my Export part. Since all my DI mappings are defined in the way of properties (getter and setters), I created a base class like this:</p> <pre><code>public class ComponentExporterBase: IDisposable { private List<IDisposable> _list; public ComponentExporterBase() { _list = new List<IDisposable>(); } protect void Add(IDisposable obj) { _list.Add(obj); } protected virtual void Dispose(bool disposing) { if (disposing) { foreach(var obj in _list) { obj.Dispose(); } _list.Clear(); } } public void Dispose() { Dispose(true); } } </code></pre> <p>With this base class, my mapping classes will be able to let MEF to do the disposing job. For example, here is one example:</p> <pre><code>internal class MyDIMappingClass : ComponentExporterBase { [Import] private IDataReader _dataReader { get; set; } [Export] private IController { get { var reader = _dataReader; var instance = new MyMainController(reader); base.Add(instance); return instance; } ... } </code></pre> <p>All my mapping classes are defined in the similar way, and they are much cleaner. The basic principle is that instances or resources which are created within a class should be disposed within the class, but not injected instances. In this way, I don't need to clean up any injected instances by MEF any more, as in this example:</p> <pre><code>public class MyMainController : IController { private IDataReader _dataReader; // dataReader is injected through CTOR public MyMainControler(IDataReader dataReader) { _dataReader = dataReader; ... } ... public void Dispose() { // dispose only resources created in this class // _dataReader is not disposed here or within the class! ...} } </code></pre> <p>By the way, I like to use properties as my imports and exports since the attributes have nothing to do a class' business logic. In other many cases, some classes are from third parties and I don't have access to their source codes to mark them as export.</p>

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