Caliburn Micro的DisplayRootViewFor中的System.NullReferenceException

Question

我正在尝试将Event Aggregator集成到我的应用程序中，并遵循在线文档，但我还无法使其完全正常运行，也无法找到完整的示例进行查看。我尝试构建的应用程序是一个用于我们内部知识库的简单搜索引擎，因此它只有3个视图-主搜索页面（根页面），结果页面和详细信息页面。

下面，我刚刚添加了我认为到目前为止调试该错误的相关代码，我正在构建该错误。如果您需要更多片段，则非常乐意提供！

诚然，我真的不知道引导程序是如何工作的-到目前为止一直在遵循教程和文档。

我的代码如下：

Bootstrapper.cs

namespace CleverBot
{
    class Bootstrapper : BootstrapperBase
    {
        private readonly SimpleContainer _container = new SimpleContainer();
        public Bootstrapper()
        {
            Initialize();
        }

        protected override void OnStartup(object sender, StartupEventArgs e)
        {
            base.OnStartup(sender, e);
            DisplayRootViewFor<ShellViewModel>();
        }

        protected override void Configure()
        {
            _container.Singleton<IEventAggregator, EventAggregator>();
            _container.RegisterPerRequest(typeof(DetailedDocumentViewModel), null, typeof(DetailedDocumentViewModel));
            _container.RegisterPerRequest(typeof(SearchPageViewModel), null, typeof(SearchPageViewModel));
            _container.RegisterPerRequest(typeof(SearchResultsViewModel), null, typeof(SearchResultsViewModel));
            _container.RegisterPerRequest(typeof(ShellViewModel), null, typeof(ShellViewModel));

        }
        protected override object GetInstance(Type serviceType, string key)
        {
            return _container.GetInstance(serviceType, key);
        }

        protected override IEnumerable<object> GetAllInstances(Type serviceType)
        {
            return _container.GetAllInstances(serviceType);
        }

        protected override void BuildUp(object instance)
        {
            _container.BuildUp(instance);
        }
    }
}

而且我的ShellViewModel.cs看起来像这样：

namespace CleverBot.ViewModels
{
    public class ShellViewModel : Conductor<object>
    {
        private readonly IEventAggregator _eventAggregator;
        public ShellViewModel(IEventAggregator eventAggregator)
        {
            _eventAggregator = eventAggregator;
            Startup.Init<SolrModel>("http://localhost:8983/solr/brain_drive");
            ShowSearchPage();
        }

        public void ShowSearchPage()
        {
            ActivateItem(new SearchPageViewModel(_eventAggregator));
        }

    }
}

最后，我的SearchPageViewModel.cs看起来像：

namespace CleverBot.ViewModels
{
    public class SearchPageViewModel : PropertyChangedBase
    {
        private string _searchTerm;
        private readonly IEventAggregator _eventAggregator;

        public SearchPageViewModel(IEventAggregator eventAggregator)
        {
            _eventAggregator = eventAggregator;
        }

        public string SearchTerm
        {
            get { return _searchTerm; }
            set
            {
                _searchTerm = value;
                NotifyOfPropertyChange(() => SearchTerm);
            }
        }
        public void BasicSearchButton()
        {
            // Build the new query object
            var queryResult = new SolrQuery(_searchTerm);

            // Execute the query, while also applying all the options
            var Result = ExecuteQuery(queryResult);

            // Publish the result, to be picked up by SearchResults VM
            _eventAggregator.PublishOnUIThread(Result);
        }

        private SolrQueryResults<SolrModel> ExecuteQuery(SolrQuery query)
        {
            var solr = CommonServiceLocator.ServiceLocator.Current.GetInstance<ISolrOperations<SolrModel>>();

            QueryOptions options = getQueryOptions();

            var docs = solr.Query(query, options);

            return docs;
        }

        private QueryOptions getQueryOptions()
        {
            var facetPivotQuery = new SolrFacetPivotQuery()
            {
                Fields = new[] { new PivotFields("created_year", "created_month") },
                MinCount = 1
            };

            QueryOptions options = new QueryOptions
            {
                Facet = new FacetParameters
                {
                    Queries = new ISolrFacetQuery[]
                    {
                        new SolrFacetFieldQuery("type"),
                        new SolrFacetFieldQuery("source"),
                        facetPivotQuery
                    }
                },
                Highlight = new HighlightingParameters
                {
                    Fields = new[] { "text", "id", "author" },
                    Fragsize = 150,
                    Snippets = 200,
                    MaxAnalyzedChars = -1
                }
            };

            return options;
        }
    }
}

有人能够阐明为什么我遇到System.NullReferenceException错误吗？我知道这是什么意思，但是我不了解如何从此框架开始就得到它。

提前感谢！

Answer 1

看来我必须注册以下内容：

_container.Singleton<IWindowManager, WindowManager>();

在我的bootstrapper.cs中，现在看起来像：

namespace CleverBot
{
    class Bootstrapper : BootstrapperBase
    {
        private SimpleContainer _container = new SimpleContainer();
        public Bootstrapper()
        {
            Initialize();
        }

        protected override void OnStartup(object sender, StartupEventArgs e)
        {
            DisplayRootViewFor<ShellViewModel>();
        }

        protected override void Configure()
        {
            _container.Singleton<IEventAggregator, EventAggregator>();

            // THE FOLLOWING WAS ADDED
            _container.Singleton<IWindowManager, WindowManager>();

            GetType().Assembly.GetTypes()
                .Where(type => type.IsClass)
                .Where(type => type.Name.EndsWith("ViewModel"))
                .ToList()
                .ForEach(viewModelType => _container.RegisterPerRequest(
                    viewModelType, viewModelType.ToString(), viewModelType));

        }
        protected override object GetInstance(Type serviceType, string key)
        {
            return _container.GetInstance(serviceType, key);
        }

        protected override IEnumerable<object> GetAllInstances(Type serviceType)
        {
            return _container.GetAllInstances(serviceType);
        }

        protected override void BuildUp(object instance)
        {
            _container.BuildUp(instance);
        }
    }
}