MEF聲明匯入

聲明匯入
以下內容從http://mef.codeplex.com/摘抄而來

屬性匯入
用Import標示組件作為屬性匯入
class Program
  {
    [Import]
    public IMessageSender MessageSender { get; set; }
  }

構造器參數匯入
通過將組件作為構造參數來實現匯入
使用方法：
 1、添加ImportingConstructor屬性
 2、為匯入添加構造參數
class Program
  {
    [ImportingConstructor]
    public Program(IMessageSender messageSender)
    {
       ...
    }
  }

參數匯入
class Program
  {
    [ImportingConstructor]
    public Program(IMessageSender messageSender)
    {
    }
  }

欄位匯入
  class Program
  {
    [Import]
    private IMessageSender _messageSender;
  }

隨意匯入
[Export]
public class OrderController {
  private ILogger _logger;

  [ImportingConstructor]
  public OrderController([Import(AllowDefault=true)] ILogger logger) {
    if(logger == null)
      logger = new DefaultLogger();
    _logger = logger;
  }
}

集合匯入
使用 ImportMany 屬性
public class Notifier
 {
    [ImportMany(AllowRecomposition=true)]
    public IEnumerable<IMessageSender> Senders {get; set;}

    public void Notify(string message)
    {
      foreach(IMessageSender sender in Senders)
      {
        sender.Send(message);
      }
    }
  }

IPartImportsSatisfiedNotification
public class Program : IPartImportsSatisfiedNotification
 {
    [ImportMany]
    public IEnumerable<IMessageSender> Senders {get; set;}

    public void OnImportsSatisfied()
    {
      // when this is called, all imports that could be satisfied have been

satisfied.
    }
  }