我刚刚开始将 Catel 用于 WPF 应用程序，但遇到了一些问题。
1）当按钮无法执行时，我没有看到该按钮按照文档显示为灰色。
2）我在哪里将代码保存到数据库中 - 在 ViewModel 或 Model 中。有没有任何地方的例子？
3) 是否有在主页中使用菜单并在单击菜单项时加载用户控件的示例？
4) 当我在 ViewModel 的构造函数中设置 DeferValidationUntilFirstSaveCall = true 时，当对话框窗口出现时出现异常。异常如下
System.NullReferenceException was unhandled by user code
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=Catel.MVVM
StackTrace:
at Catel.Windows.Data.Converters.GetFirstValidationErrorConverter.Convert(Object value, Type targetType, Object parameter)
at Catel.Windows.Data.Converters.ValueConverterBase.Convert(Object value, Type targetType, Object parameter, CultureInfo culture)
at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
at System.Windows.Data.BindingExpression.Activate(Object item)
at System.Windows.Data.BindingExpression.AttachToContext(AttachAttempt attempt)
at System.Windows.Data.BindingExpression.AttachOverride(DependencyObject target, DependencyProperty dp)
at System.Windows.Data.BindingExpressionBase.OnAttach(DependencyObject d, DependencyProperty dp)
at System.Windows.StyleHelper.GetInstanceValue(UncommonField`1 dataField, DependencyObject container, FrameworkElement feChild, FrameworkContentElement fceChild, Int32 childIndex, DependencyProperty dp, Int32 i, EffectiveValueEntry& entry)
at System.Windows.StyleHelper.GetChildValueHelper(UncommonField`1 dataField, ItemStructList`1& valueLookupList, DependencyProperty dp, DependencyObject container, FrameworkObject child, Int32 childIndex, Boolean styleLookup, EffectiveValueEntry& entry, ValueLookupType& sourceType, FrameworkElementFactory templateRoot)
at System.Windows.StyleHelper.GetChildValue(UncommonField`1 dataField, DependencyObject container, Int32 childIndex, FrameworkObject child, DependencyProperty dp, FrugalStructList`1& childRecordFromChildIndex, EffectiveValueEntry& entry, ValueLookupType& sourceType, FrameworkElementFactory templateRoot)
at System.Windows.StyleHelper.GetValueFromStyleOrTemplate(FrameworkObject fo, DependencyProperty dp, EffectiveValueEntry& entry)
at System.Windows.StyleHelper.ApplyStyleOrTemplateValue(FrameworkObject fo, DependencyProperty dp)
at System.Windows.StyleHelper.InvalidateContainerDependents(DependencyObject container, FrugalStructList`1& exclusionContainerDependents, FrugalStructList`1& oldContainerDependents, FrugalStructList`1& newContainerDependents)
at System.Windows.StyleHelper.DoStyleInvalidations(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle)
at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache)
at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.Controls.TextBox.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp, Boolean preserveCurrentValue)
at System.Windows.FrameworkElement.UpdateStyleProperty()
at System.Windows.FrameworkElement.OnInitialized(EventArgs e)
at System.Windows.FrameworkElement.TryFireInitialized()
at System.Windows.FrameworkElement.EndInit()
at MS.Internal.Xaml.Runtime.ClrObjectRuntime.InitializationGuard(XamlType xamlType, Object obj, Boolean begin)
at MS.Internal.Xaml.Runtime.PartialTrustTolerantRuntime.InitializationGuard(XamlType xamlType, Object obj, Boolean begin)
at System.Xaml.XamlObjectWriter.Logic_EndInit(ObjectWriterContext ctx)
at System.Xaml.XamlObjectWriter.WriteEndObject()
at System.Xaml.XamlWriter.WriteNode(XamlReader reader)
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.LoadComponent(Object component, Uri resourceLocator)
at FNZCIressClient.Views.AccountMappingWindow.InitializeComponent() in h:\Documents\iress-utils\FNZCIressClient\FNZCIressClient\Views\AccountMappingWindow.xaml:line 1
at FNZCIressClient.Views.AccountMappingWindow..ctor(AccountMappingViewModel viewModel) in h:\Documents\iress-utils\FNZCIressClient\FNZCIressClient\Views\AccountMappingWindow.xaml.cs:line 28
InnerException:
如果我从代码中删除 defervalidation 行，则弹出窗口有效。
任何帮助和建议表示赞赏。