试图找出MEF合成错误意味着什么

Question

对于试图完成对.ComposeParts(this)的调用的以下异常，我有一个问题：

合成产生一个单一的合成错误。根本原因如下。查看CompositionException.Errors属性以获得更详细的信息。

1)输出'CustomersModule.CustomerMenu (ContractName=‘ModLibrary.IMenu’)不能指定为ModLibrary、Version=1.0.0.0、Culture=neutral、PublicKeyToken=null‘’。

结果:无法在部件'ModAppWorks.Host‘上设置导入'ModAppWorks.Host.Menus (ContractName=“ModLibrary.IMenu”)。元素: ModAppWorks.Host.Menus (ContractName="ModLibrary.IMenu") -> ModAppWorks.Host

其中有一部分似乎是错误意味着IMenu必须实现IEnumerable。这是我的作文代码：

static class Program
{
    [STAThread]
    static void Main()
    {
        Host host = new Host();
        host.Run();
    }
}

class Host
{
    #region Init
    public Host()
    { }
    #endregion

    #region Functions
    public void Run()
    {
        Compose();

        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new AppHost());
    }

    private void Compose()
    {
        var agrCatalog = new AggregateCatalog();
        var dirCatalog = new DirectoryCatalog(Path.GetDirectoryName
            (Assembly.GetExecutingAssembly().Location) + "..\\..\\..\\Extensions", "*.dll");
        var asmCatalog = new AssemblyCatalog(Assembly.GetExecutingAssembly());

        agrCatalog.Catalogs.Add(dirCatalog);
        agrCatalog.Catalogs.Add(asmCatalog);

        var hostContainer = new CompositionContainer(agrCatalog);
        hostContainer.ComposeParts(this);
    }
    #endregion

    #region Properties
    [Import(typeof(IMenu))]
    public IEnumerable<IMenu> Menus { get; set; }
    #endregion

我正在导入一个实例为ToolStripMenuItem的类。我的出口样品：

[Export(typeof(IMenu))]
public class CustomerMenu : IMenu
{
    #region Fields
    private System.Windows.Forms.ToolStripMenuItem CustomerMainMenu;
    private System.Windows.Forms.ToolStripSeparator mnuSeparator;
    private System.Windows.Forms.ToolStripMenuItem CustomersMenuItem;
    #endregion

    #region Init
    public CustomerMenu()
    {
        InitializeComponent();
        // 
        // CustomerMenu
        // 
        this.CustomerMainMenu.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
        this.mnuSeparator,
        this.CustomersMenuItem});
        this.CustomerMainMenu.Name = "CustomerMenu";
        this.CustomerMainMenu.Size = new System.Drawing.Size(94, 20);
        this.CustomerMainMenu.Text = "Customer Menu";
        // 
        // toolStripMenuItem1
        // 
        this.mnuSeparator.Name = "toolStripMenuItem1";
        this.mnuSeparator.Size = new System.Drawing.Size(149, 6);
        // 
        // Customers
        // 
        this.CustomersMenuItem.Name = "Customers";
        this.CustomersMenuItem.Size = new System.Drawing.Size(152, 22);
        this.CustomersMenuItem.Text = "Customers";
    }

    #endregion

    #region Functions
    private void InitializeComponent()
    {
        this.CustomerMainMenu = new System.Windows.Forms.ToolStripMenuItem();
        this.mnuSeparator = new System.Windows.Forms.ToolStripSeparator();
        this.CustomersMenuItem = new System.Windows.Forms.ToolStripMenuItem();
    }

    #endregion

如果不需要IMenu实现IEnumerable，是否有人看到我可能做错了什么？

Answer 1

在导入导出集合时，需要使用ImportMany属性对其进行显式说明。更改属性属性如下：

[ImportMany(typeof(IMenu))] 
public IEnumerable<IMenu> Menus { get; set; } 

您还应该能够排除契约(“type (菜单)”参数)，因为您导入的是导出的相同类型。不过，将合同保留在Export上。

[ImportMany] 
public IEnumerable<IMenu> Menus { get; set; }