Question

我想在ClassLibrary中使用MEF，而不是在应用程序项目中使用MEF（ConsoleApplication和WebApplication ......）。

当我尝试这样做时（如MSDN：http://msdn.microsoft.com/en-us/library/dd460648.aspx）

class Program
{
    private CompositionContainer _container;

    [Import(typeof(IPlugin))]
    public IPlugin Plugins;


    private Program()
    {
        //An aggregate catalog that combines multiple catalogs
        var catalog = new AggregateCatalog();
        //Adds all the parts found in the same assembly as the Program class
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(Program).Assembly));
        catalog.Catalogs.Add(new DirectoryCatalog(@".\Extensions"));


        //Create the CompositionContainer with the parts in the catalog
        _container = new CompositionContainer(catalog);

        //Fill the imports of this object
        try
        {
            this._container.ComposeParts(this);
        }
        catch (CompositionException compositionException)
        {
            Console.WriteLine(compositionException.ToString());
        }
    }


    static void Main(string[] args)
    {
        Program p = new Program(); //Composition is performed in the constructor
    }
}

财产：

    [Import(typeof(IPlugin))]
    public IPlugin Plugins;

工作正常。

编辑：

但是，我想移动进口物业＆amp; ClassLibrary中的聚合目录创建，而不是我的ConsoleApplication中的聚合目录创建。

如下所示。

在ClassLibrary [Manager.dll]中：

public class Manager
{
    private CompositionContainer _container;

    [Import(typeof(IPlugin))]
    public IPlugin Plugins;


    public Manager()
    {
        //An aggregate catalog that combines multiple catalogs
        var catalog = new AggregateCatalog();
        //Adds all the parts found in the same assembly as the Program class
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(Manager).Assembly));
        catalog.Catalogs.Add(new DirectoryCatalog(@".\Extensions"));


        //Create the CompositionContainer with the parts in the catalog
        _container = new CompositionContainer(catalog);

        //Fill the imports of this object
        try
        {
            this._container.ComposeParts(this);
        }
        catch (CompositionException compositionException)
        {
            Console.WriteLine(compositionException.ToString());
        }
    }
}

在ConsoleApplication中：

class Manager
{
    static void Main(string[] args)
    {
        Manager m = new Manager(); //Composition is performed in the constructor
    }
}

但是当我做这个改变时，我无法获得在我的ClassLibrary中始终为“null”的“插件”属性。

任何人都有解决方案吗？

Answer 1

这可能只是您的目录的一个问题。如果要将属性移动到类库中，则意味着单独的程序集。目前，只有托管“程序”的程序集在您的目录中，以及“扩展程序”中的任何内容。那么，你确定你的新类库在扩展文件夹中吗？

此外，您正在编写this，这意味着您正在编写“程序”的实例。如果您将属性移动到不同库中的其他类，则需要编写任何类的实例。

这样的事情：

    class Program
   {
    private CompositionContainer _container;       

    private Program()
    {
        var helper = new MyOtherHelperClass();
        var catalog = helper.CreateCatalog();

        //Create the CompositionContainer with the parts in the catalog
        _container = new CompositionContainer(catalog);

        //Fill the imports of some object
        try
        {
            var thingIWantToCompose = new OtherClassWithAnImport();
            this._container.ComposeParts(thingIWantToCompose);
        }
        catch (CompositionException compositionException)
        {
            Console.WriteLine(compositionException.ToString());
        }
    }


    static void Main(string[] args)
    {
        Program p = new Program(); //Composition is performed in the constructor
    }
}

如果不起作用，请尝试在Visual MEFX中查看您的部件。以下是设置简短指南：Getting Started with Visual MEFX

在类库中使用MEF

1 个答案: