主要是利用AppDomain的ShadowCopy特性。

        var setup = new AppDomainSetup
        {
            CachePath = cachePath,
            ShadowCopyFiles = "true",
            ShadowCopyDirectories = pluginPath
        };

之后创建程序集

        domain = AppDomain.CreateDomain("Host_AppDomain", AppDomain.CurrentDomain.Evidence, setup);
        var asmfullname = typeof(UseConfig).Assembly.FullName;
        var typefullname = typeof(UseConfig).FullName;
        useConfig = (UseConfig)domain.CreateInstanceAndUnwrap(asmfullname, typefullname);
        useConfig.Build();

在创建好的程序集里通过MEF加载插件

    useConfig.cs:
    public void Build()
    {
        var regBuilder = new RegistrationBuilder();
        regBuilder.ForTypesDerivedFrom<IConfig>().Export<IConfig>();

        var catalog = new AggregateCatalog();
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(UseConfig).Assembly, regBuilder));
        directoryCatalog = new DirectoryCatalog(pluginPath, regBuilder);
        catalog.Catalogs.Add(directoryCatalog);

        container = new CompositionContainer(catalog);
        container.ComposeExportedValue(container);

        configs = container.GetExportedValues<IConfig>();
    }

替换插件有两种情况

1. 先删除后添加
   刷新一下，重新输出。
   public void Recompose()
   {
   directoryCatalog.Refresh();
   container.ComposeParts(directoryCatalog.Parts);
   configs = container.GetExportedValues<IConfig>();
   }

2. 直接替换
   通过FileWatch监视，一旦有文件变化Unload AppDomain，然后重新加载。