Xceed PropertyGrid与System.Windows.Media.Color []抛出NullReferenceException

Question

我有一个对象，我试图用PropertyGrid和它尝试访问Color []属性时引发NullReferenceException。

堆栈跟踪看起来像：

System.NullReferenceException: Object reference not set to an instance of an object. 
    at Xceed.Wpf.Toolkit.CollectionControlDialog.Clone(Object source) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlDialog.xaml.cs:line 168 
    at Xceed.Wpf.Toolkit.CollectionControlDialog.OnSourceInitialized(EventArgs e) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlDialog.xaml.cs:line 137 
    at System.Windows.Window.CreateSourceWindow(Boolean duringShow) 
    at System.Windows.Window.CreateSourceWindowDuringShow() 
    at System.Windows.Window.SafeCreateWindowDuringShow() 
    at System.Windows.Window.ShowHelper(Object booleanBox) 
    at System.Windows.Window.Show() 
    at System.Windows.Window.ShowDialog() 
    at Xceed.Wpf.Toolkit.CollectionControlButton.CollectionControlButton_Click(Object sender, RoutedEventArgs e) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlButton.cs:line 124 
    at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) 
    at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) 
    at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args) 
    at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e) 
    at System.Windows.Controls.Primitives.ButtonBase.OnClick() 
    at System.Windows.Controls.Button.OnClick() 
    at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e) 
    at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e) 
    at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) 
    at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target) 
    at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) 
    at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) 
    at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent) 
    at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e) 
    at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) 
    at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target) 
    at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) 
    at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) 
    at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args) 
    at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args) 
    at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted) 
    at System.Windows.Input.InputManager.ProcessStagingArea() 
    at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input) 
    at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport) 
    at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel) 
    at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled) 
    at System.Windows.Interop.HwndSource.InputFilterMessage(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) 

正如你所看到的，没有什么与我自己的代码，所以这一定是一个相当常见的错误。它看起来像试图克隆我的Color对象数组并失败，但数组和内部的对象均为null。

有什么想法？

Answer 1

这是CollectionControlDialog类中的一个错误。

在方法Clone()中，它们获取提供的集合项的类型，然后尝试调用该类型的默认构造函数。我想，他们想要创建每个收集项目的深层副本。

但显然，一个structColor没有默认的构造函数（作为一种方法），它可以通过反射获得。 （您可以在struct上使用的默认无参数构造函数实际上不是构造函数，但它是运行时如何创建struct的默认实例的IL指令）。

所以这就是为什么GetConstructor()方法返回null，并试图调用一个null的方法抛出NullReferenceException你观察。

你可以列出一个错误或自己修复它，并承诺到Xceed存储库。

目前，这个bug会阻止您能够与不具有默认参数的构造函数这样的对象（如struct S或一些class ES太）使用CollectionControlDialog。