Question

我在WPF中使用Prism。当我将IEventAggregator作为参数添加到ViewModel构造函数时，我收到此错误： Microsoft.Practices.ServiceLocation.dll中发生类型“Microsoft.Practices.ServiceLocation.ActivationException”的异常。其他信息：尝试获取Object类型的实例时出现激活错误，键“CategoriesView”

此行触发了异常：

private void NavigateToCategoriesRadioButton_Click(object sender, RoutedEventArgs e)
{
    this.regionManager.RequestNavigate(RegionNames.ConfigurationContentRegion, categoriesViewUri);
}

其中categoriesViewUri是：

private static Uri categoriesViewUri = new Uri("/CategoriesView", UriKind.Relative);

这是我的视图模型类：

[Export]
public class CategoriesViewModel : BindableBase
{
    private readonly IRegionManager regionManager;
    private readonly IEventAggregator eventAggregator;
    private readonly IConfigurationCategoriesService categoriesService;
    private readonly ObservableCollection<Category> categoriesCollection;
    private readonly ICollectionView categoriesView;
    private readonly DelegateCommand<object> deleteCategoryCommand;

    [ImportingConstructor]
    public CategoriesViewModel(IEventAggregator eventAggregator, IConfigurationCategoriesService categoriesService, IRegionManager regionManager)
    {    
        this.categoriesService = categoriesService;
        this.regionManager = regionManager;
        this.eventAggregator = eventAggregator;

        this.deleteCategoryCommand = new DelegateCommand<object>(this.DeleteCategory, this.CanDeleteCategory);

        this.categoriesCollection = new ObservableCollection<Category>(categoriesService.GetCategories());
        this.categoriesView = new ListCollectionView(this.categoriesCollection);
        this.categoriesView.CurrentChanged += (s, e) => this.deleteCategoryCommand.RaiseCanExecuteChanged();

    }

    public ICollectionView Categories
    {
        get { return this.categoriesView; } 
    }

    public ICommand DeleteCategoryCommand
    {
        get { return this.deleteCategoryCommand; }
    }

    private void DeleteCategory(object ignored)
    {
        var category = this.categoriesView.CurrentItem as Category;
        if (category != null)
        {
            categoriesService.DeleteCategory(category);
        }
    }
    private bool CanDeleteCategory(object ignored)
    {
        return true;
    }
}

看起来CatagoriesViewModel无法在构造函数上获取IEventAggregator的实例，但这是由Prism自动完成的，不是吗？在我从Prism Documentation（StockTraderRI_Desktop）获得的示例中，我没有看到EventAggregator被实例化的任何地方。任何人都可以看到我错了什么？提前致谢

Editted：

Navitagion项目视图在CategoriesModule类中注册：

[ModuleExport(typeof(CategoriesModule))]
public class CategoriesModule : IModule
{
    [Import]
    public IRegionManager regionManager;

    public void Initialize()
    {
        this.regionManager.RegisterViewWithRegion(RegionNames.ConfigurationNavigationRegion, typeof(CategoriesNavigationItemView));
    }
}

和CategoriesView代码隐藏是：

[Export("CategoriesView")]
public partial class CategoriesView : UserControl
{
    public CategoriesView()
    {
        InitializeComponent();
    }

    [Import]
    public IRegionManager regionManager;

    [Import]
    public CategoriesViewModel ViewModel
    {
        get { return this.DataContext as CategoriesViewModel; }
        set { this.DataContext = value; }
    }
}

Answer 1

我解决了这个问题，添加了以下using语句：

using Microsoft.Practices.Prism.PubSubEvents;

而不是

using Prism.Events;

我也通过本网站的推荐切换到Unity而不是MEF。

IEventAggregator Prism激活错误

1 个答案: