XAML 中 Ninject 中的 NullReferenceException

Question

我刚刚开始使用 Ninject (3.2.2.0) 作为我的 MVVM 项目的 DI。到目前为止，我的实现非常简单——没有接口与 Ninject 一起使用，只为 ViewModel 做 DI。当处理 MainWindow 的 XAML 时，我得到一个 NullReferenceException。 View 和 ViewModel 的构造函数在 NRE 之前成功完成。 App.OnStartup() 完成后发生异常。这里是 App.xaml.cs:

namespace PSS
{
    public partial class App : Application
    {
        private IKernel Container;

        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            Container = new StandardKernel();
            Application.Current.MainWindow = Container.Get<MainWindow>();
            Application.Current.MainWindow.Show();
        }
    }
}

这里是 MainWindow.xaml.cs:

namespace PSS
{
    public partial class MainWindow : Window
    {
        public MainWindow(MainWindowVM viewModel)
        {
            DataContext = viewModel;
            InitializeComponent();
            Messenger.Default.Register<string>(this, UICommands);
            CMTextBox.Focus();
        }
    }
}

关于为什么 XAML 中的某些内容显然没有被初始化，有什么建议吗？我确实在 XAML 中使用了几个 IValueConverter，但是当我删除它们的引用时，NRE 仍然会发生。

编辑：NRE 的堆栈跟踪：

System.NullReferenceException was unhandled
  _HResult=-2147467261
  _message=Object reference not set to an instance of an object.
  HResult=-2147467261
  IsTransient=false
  Message=Object reference not set to an instance of an object.
  Source=mscorlib
  StackTrace:
   at System.DefaultBinder.BindToMethod(BindingFlags bindingAttr, MethodBase[] match, Object[]& args, ParameterModifier[] modifiers, CultureInfo cultureInfo, String[] names, Object& state)
   at MS.Internal.Xaml.Runtime.DynamicMethodRuntime.CreateInstanceWithCtor(Type type, Object[] args)
   at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CreateInstance(XamlType xamlType, Object[] args)
   at System.Xaml.XamlObjectWriter.Logic_CreateAndAssignToParentStart(ObjectWriterContext ctx)
   at System.Xaml.XamlObjectWriter.WriteStartMember(XamlMember property)
   at System.Windows.Markup.WpfXamlLoader.TransformNodes(XamlReader xamlReader, XamlObjectWriter xamlWriter, Boolean onlyLoadOneNode, Boolean skipJournaledProperties, Boolean shouldPassLineNumberInfo, IXamlLineInfo xamlLineInfo, IXamlLineInfoConsumer xamlLineInfoConsumer, XamlContextStack`1 stack, IStyleConnector styleConnector)
   at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
   at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
   at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
   at System.Windows.Application.LoadBamlStreamWithSyncInfo(Stream stream, ParserContext pc)
   at System.Windows.Application.DoStartup()
   at System.Windows.Application.<.ctor>b__1_0(Object unused)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at PSS.App.Main() in c:\Users\conrad\VSSolutions\Measurements\PSS\obj\Debug\App.g.cs:line 0
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Answer 1

我刚遇到与 microsoft.extensions.dependencyinjection

相同的问题

在研究过程中，我发现如果重写 OnStartup 方法，我应该从 App.xaml 中删除 StartupUri为我解决了这个问题。

既然你也在重写OnStartup，我相信它也会为你解决。

XAML 中 Ninject 中的 NullReferenceException

NullReferenceException in Ninject in XAML

xaml

ninject

mvvm

nullreferenceexception