如果在目录中发现新的DLL,则对DirectoryCatalog调用Refresh()会抛出ChangeRejectedException

我在做实验 MEF

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ProbeContract
{
    public interface IProbe
    {
        int DoProbe(string what);
        List<string> GetCapabilities();
    }
}

我创建了一个示例控制台程序,该程序从其自己的程序集中加载“插件”,如果找到任何插件,则从其中放置其他DLL的目录中加载。无论插件目录为空(仅调用“本机”插件)还是具有兼容的DLL,程序都能正常工作。但是。..如果在循环迭代之间添加了一个新的DLL,DirectoryCatalog的Refresh()方法会抛出一个ChangeRejectedException,解释如下:

组成保持不变。这 由于以下原因,更改被拒绝 产生了一个单一的构图错误。 根本原因如下。

(合同名称=“ProbeConstructor.IProbe”)'

程序如下,后面是我尝试添加的DLL的代码。我做错了什么?

using System;
using System.IO;
using System.Reflection;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ProbeContract;
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Hosting;

namespace MEFTest
{
    class Program
    {
        [ImportMany]
        IEnumerable<IProbe> ProberSet { get; set; }

        CompositionContainer exportContainer;
        DirectoryCatalog pluginCatalog;
        AggregateCatalog catalog;

        private void Run()
        {
            catalog = new AggregateCatalog();
            catalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
            string myExecName = Assembly.GetExecutingAssembly().Location;
            string myPath = Path.GetDirectoryName(myExecName);
            pluginCatalog = new DirectoryCatalog(myPath + "/Plugins");
            catalog.Catalogs.Add(pluginCatalog);
            exportContainer = new CompositionContainer(catalog);

            CompositionBatch compBatch = new CompositionBatch();
            compBatch.AddPart(this);
            compBatch.AddPart(catalog);
            exportContainer.Compose(compBatch);

            for (; ; )
            {
                Console.Write("Press any key to run all probes: ");
                Console.ReadKey(true);
                Console.WriteLine();
                pluginCatalog.Refresh();
                foreach (var Prober in ProberSet)
                {
                    Prober.DoProbe("gizmo");
                }
            }
        }

        static void Main(string[] args)
        {
            Program p = new Program();
            p.Run();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel.Composition;
using ProbeContract;

namespace OtherProbes
{
    [Export(typeof(IProbe))]
    public class SpankyNewProber : IProbe
    {
        public int DoProbe(string what)
        {
            Console.WriteLine("I'm Spanky and New and I'm probing [{0}]", what);
            return 0;
        }

        public List<string> GetCapabilities()
        {
            List<string> retVal = new List<string>();
            retVal.Add("spanky");
            retVal.Add("new");
            return retVal;
        }
    }
}