类型或命名空间名称''；未能找到(是否缺少using指令或程序集引用?)

这项工作对于我正在转移到这个应用程序中的另一个应用程序来说很好。我已经被困在这里几个小时了，谷歌没有太多的MEF。System.ComponentModel.Composition.dll已导入，是的。但仍然无法摆脱这个错误。

我有这个为我的包括：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.ComponentModel.Composition;
using JSNet;

受影响的代码：

var catalog = new AggregatingComposablePartCatalog();
var mainAssemblyCatalog = new AttributedAssemblyPartCatalog(this.GetType().Assembly);
var jsNetCatalog = new AttributedAssemblyPartCatalog(typeof(Effect).Assembly);            
//var addInEffects = new DirectoryPartCatalog("Effects"); 
catalog.Catalogs.Add(mainAssemblyCatalog);
catalog.Catalogs.Add(jsNetCatalog);
//catalog.Catalogs.Add(addInEffects);
var container = new CompositionContainer(catalog);

错误：

Error 1: The type or namespace name 'AggregatingComposablePartCatalog' could not be found (are you missing a using directive or an assembly reference?) 
Error 2: The type or namespace name 'AttributedAssemblyPartCatalog' could not be found (are you missing a using directive or an assembly reference?)    
Error 3: The type or namespace name 'AttributedAssemblyPartCatalog' could not be found (are you missing a using directive or an assembly reference?)    
Error 4: The type or namespace name 'CompositionContainer' could not be found (are you missing a using directive or an assembly reference?)