Question

所以我试图用一个并排的用户控件创建一个应用程序，当你在它们之间切换时，它会左右滑动。问题是，我的一个用户控件（AddReferencePage），当添加到MainWindow时，导致我的MainWindow上的开始标记变为带有NullReferenceException错误的下划线。设计师还显示错误：

NullReferenceException: Object reference not set to an instance of an object.

StackTrace:
 at ARC.AddReferencePage.ReferenceDetails()
at ARC.AddReferencePage.AddReferencePage_Loaded(Object sender, RoutedEventArgs e)
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.BroadcastEventHelper.BroadcastEvent(DependencyObject root, RoutedEvent routedEvent)
at System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(Object root)
at MS.Internal.LoadedOrUnloadedOperation.DoWork()
at System.Windows.Media.MediaContext.FireLoadedPendingCallbacks()
at System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler

显示我的用户控件的代码是：

<DockPanel x:Name="SlideGrid" VerticalAlignment="Stretch" Width="{Binding ActualWidth, ElementName=MainGrid, Converter={StaticResource DoubleConverter}}" Margin="0,28,0,0" ClipToBounds="True">
    <ItemsControl DockPanel.Dock="Left">
        <local:MainPage/>
    </ItemsControl>
    <ItemsControl DockPanel.Dock="Right">
        <local:AddReferencePage/>
    </ItemsControl>
</DockPanel>

MainPage工作正常，没有任何错误。它是导致错误的AddReferencePage。我已经检查了每个用户控件各自的代码隐藏，并且它们的目的和目的完全相同。

MainPage的代码隐藏：

Imports System.Collections.ObjectModel
Imports System.ComponentModel
Imports System.Collections.Specialized
Imports System.Windows.Threading
Imports System.Windows.Media.Animation
Imports System.Globalization

Public Class MainPage
Private StartPoint As Point

Private Sub MainPage_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
    'Dim PW As MainWindow = Window.GetWindow(MainPage)
    'If PW IsNot Nothing Then
    '    ReferenceList.ItemsSource = PW.ReferenceCollection
    '    Dim Alphabetical As SortDescription = New SortDescription("PropLastName", ListSortDirection.Ascending)
    '    ReferenceList.Items.SortDescriptions.Add(Alphabetical)
    'End If
    RefreshReferences()
End Sub

Public Sub RefreshReferences()
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    If PW IsNot Nothing Then
        ReferenceList.ItemsSource = PW.ReferenceCollection
        Dim Alphabetical As SortDescription = New SortDescription("PropLastName", ListSortDirection.Ascending)
        ReferenceList.Items.SortDescriptions.Add(Alphabetical)
    End If
End Sub

Private Sub ListBoxSearch_TextChanged(sender As Object, e As TextChangedEventArgs) Handles ListBoxSearch.TextChanged
    If ListBoxSearch.Text <> "Search..." Then
        Dim PW As MainWindow = Window.GetWindow(MainPage)
        If PW IsNot Nothing Then
            PW.view = CollectionViewSource.GetDefaultView(PW.ReferenceCollection)
            PW.view.Filter = New Predicate(Of Object)(AddressOf PW.FilterList)
        End If
    End If

End Sub

Private Sub ListBoxSearch_MouseLeftButtonUp(sender As Object, e As MouseButtonEventArgs) Handles ListBoxSearch.PreviewMouseDown
    If ListBoxSearch.Text = "Search..." Then
        ListBoxSearch.FontStyle = FontStyles.Normal
        ListBoxSearch.Clear()
    End If
End Sub


Private Sub ListBoxSearch_LostFocus(sender As Object, e As RoutedEventArgs) Handles ListBoxSearch.LostFocus
    If ListBoxSearch.Text = "" Then
        ListBoxSearch.FontStyle = FontStyles.Italic
        ListBoxSearch.Text = "Search..."
    End If
End Sub

Private Sub ListViewClick(sender As Object, e As RoutedEventArgs) Handles ButtonListView.Click
    If ReferenceList.ItemTemplate Is FindResource("GridViewTemplate") Then
        ViewBackground.BeginStoryboard(DirectCast(Me.Resources("ViewRightToLeft"), Storyboard))
        ReferenceList.ItemTemplate = DirectCast(Me.FindResource("ListViewTemplate"), DataTemplate)
        ButtonListView.Content = FindResource("NoListView")
        ButtonGridView.Content = FindResource("NoGridView")
    End If
End Sub

Private Sub GridViewClick(sender As Object, e As RoutedEventArgs) Handles ButtonGridView.Click
    If ReferenceList.ItemTemplate Is FindResource("ListViewTemplate") Then
        ViewBackground.BeginStoryboard(DirectCast(Me.Resources("ViewLeftToRight"), Storyboard))
        ReferenceList.ItemTemplate = DirectCast(Me.FindResource("GridViewTemplate"), DataTemplate)
        ButtonListView.Content = FindResource("NoListView")
        ButtonGridView.Content = FindResource("NoGridView")
    End If
End Sub

Private Sub ListViewEnter(sender As Object, e As RoutedEventArgs) Handles ButtonListView.MouseEnter

End Sub

Private Sub GridViewEnter(sender As Object, e As RoutedEventArgs) Handles ButtonGridView.MouseEnter

End Sub

Private Sub ListViewLeave(sender As Object, e As RoutedEventArgs) Handles ButtonListView.MouseLeave

End Sub

Private Sub GridViewLeave(sender As Object, e As RoutedEventArgs) Handles ButtonGridView.MouseLeave

End Sub

Private Sub EditListBoxItem(sender As Object, e As RoutedEventArgs)
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    If PW IsNot Nothing Then
        PW.ChangeSlide(sender, 1)
        PW.EditItem = ReferenceList.SelectedItem
        PW.NewItem = False
    End If
End Sub

Private Sub DeleteListBoxItem(sender As Object, e As RoutedEventArgs)
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    If PW IsNot Nothing Then
        PW.ReferenceCollection.Remove(ReferenceList.SelectedItem)
    End If
End Sub

Private Sub NewListBoxItem(sender As Object, e As RoutedEventArgs)
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    If PW IsNot Nothing Then
        PW.ChangeSlide(sender, 1)
        PW.NewItem = True
    End If
End Sub

Private Sub ReferenceList_Loaded(sender As Object, e As RoutedEventArgs) Handles ReferenceList.Loaded
    RefreshReferences()
End Sub

Private Sub ReferenceList_PreviewMouseLeftButtonDown(sender As Object, e As MouseButtonEventArgs) Handles ReferenceList.PreviewMouseLeftButtonDown
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    StartPoint = e.GetPosition(Nothing)
    PW.Resizing = False
End Sub

Private Sub ReferenceList_PreviewMouseMove(sender As Object, e As MouseEventArgs) Handles ReferenceList.PreviewMouseMove
    Dim PW As MainWindow = Window.GetWindow(MainPage)
    If PW.Resizing = False Then
        Dim MousePosition As Point = e.GetPosition(Nothing)
        Dim Difference As Vector = StartPoint - MousePosition
        Dim StopDrop As Boolean
        If e.LeftButton = MouseButtonState.Pressed AndAlso (Math.Abs(Difference.X) > SystemParameters.MinimumHorizontalDragDistance Or Math.Abs(Difference.Y) > SystemParameters.MinimumVerticalDragDistance) Then
            Dim LB As ListBox = sender
            Dim UIE As UIElement = LB.InputHitTest(MousePosition)
            If UIE IsNot Nothing Then
                Dim Data As Object = DependencyProperty.UnsetValue
                While Data Is DependencyProperty.UnsetValue And UIE IsNot Nothing
                    Data = LB.ItemContainerGenerator.ItemFromContainer(UIE)
                    If Data Is DependencyProperty.UnsetValue Then
                        UIE = VisualTreeHelper.GetParent(UIE)
                    End If
                    If UIE Is LB Then
                        StopDrop = True
                    End If
                End While
                If Data IsNot DependencyProperty.UnsetValue Then
                    StopDrop = False
                End If
            Else
                StopDrop = True
            End If
            PW.TempItem = LB.SelectedItem
            Dim FN As String = PW.TempItem.PropLastName & ", " & PW.TempItem.PropFirstName.Substring(0, 1)
            Dim TT As String = PW.TempItem.PropTitle
            Dim YR As String = PW.TempItem.PropYear.ToString
            Dim ReferenceText As String = FN & " " & YR & ", " & TT
            Dim DragData As DataObject = New DataObject(DataFormats.StringFormat, ReferenceText)
            If DragData IsNot Nothing And StopDrop = False Then
                DragDrop.DoDragDrop(sender, DragData, DragDropEffects.Copy)
            End If
        End If
    End If

End Sub
End Class

MainPage的XAML：

<UserControl x:Class="MainPage" x:Name="MainPage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:ARC"
         mc:Ignorable="d"
         VerticalAlignment="Stretch" HorizontalAlignment="Stretch" d:DesignWidth="400" d:DesignHeight="600" SnapsToDevicePixels="True">
<UserControl.Resources>
    <local:ImageConverter x:Key="ImageConverter"/>
    <Image x:Key="BrownBook" Source="Images\Icons\BrownBook.png" Height="64" Width="64"/>

    <Storyboard x:Key="ViewRightToLeft" 
                AccelerationRatio=".5"
                DecelerationRatio=".5">
        <ThicknessAnimation Storyboard.TargetName="ViewBackground" Storyboard.TargetProperty="Margin" Duration="0:0:0.15" To="0,0,28,0"/>
    </Storyboard>

    <Storyboard x:Key="ViewLeftToRight" 
                AccelerationRatio=".5"
                DecelerationRatio=".5">
        <ThicknessAnimation Storyboard.TargetName="ViewBackground" Storyboard.TargetProperty="Margin" Duration="0:0:0.15" To="0,0,-28,0"/>
    </Storyboard>
</UserControl.Resources>

<Grid Background="#FFF1F1F1">
    <Grid>
        <DockPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
            <DockPanel Margin="0,0,0,0" VerticalAlignment="Top" HorizontalAlignment="Stretch" Height="28" DockPanel.Dock="Top" Background="#E5E5E5">
                <Button BorderThickness="0" x:Name="AddNewReference" Style="{DynamicResource NoChromeButton}" DockPanel.Dock="Right" HorizontalAlignment="Right" Click="ListViewClick" Height="28" Width="28">
                    <DynamicResource ResourceKey="SearchBar"/>
                </Button>
                <Button BorderThickness="0" x:Name="Settings" Style="{DynamicResource NoChromeButton}" DockPanel.Dock="Right" HorizontalAlignment="Right" Click="ListViewClick" Height="28" Width="28">
                    <DynamicResource ResourceKey="SearchBar"/>
                </Button>
                <Grid Margin="0,0,0,0" DockPanel.Dock="Right" Width="56" Height="28" VerticalAlignment="Top" HorizontalAlignment="Stretch">
                    <Button Height="28" Width="28" Margin="0,0,28,0" BorderThickness="0" Style="{DynamicResource NoChromeButton}" x:Name="ViewBackground" Background="#3E3B3B"/>
                    <Button Margin="0,0,0,0" BorderThickness="0" x:Name="ButtonGridView" Style="{DynamicResource NoChromeButton}" HorizontalAlignment="Right" Click="GridViewClick" Height="28" Width="28">
                        <DynamicResource ResourceKey="NoGridView"/>
                    </Button>
                    <Button Margin="0,0,28,0" BorderThickness="0" x:Name="ButtonListView" Style="{DynamicResource NoChromeButton}" HorizontalAlignment="Right" Click="ListViewClick" Height="28" Width="28">
                        <DynamicResource ResourceKey="NoListView"/>
                    </Button>

                </Grid>
                <Button BorderThickness="0" x:Name="SearchBarIcon" Style="{DynamicResource NoChromeButton}" DockPanel.Dock="Left" HorizontalAlignment="Right" Click="ListViewClick" Height="28" Width="23">
                    <DynamicResource ResourceKey="SearchBar"/>
                </Button>
                <TextBox x:Name="ListBoxSearch" Style="{DynamicResource SearchBoxTemplate}" Text="Search..." FontSize="16" HorizontalAlignment="Stretch" FontStyle="Italic" BorderThickness="0" Foreground="Gray" Background="Transparent" VerticalContentAlignment="Top"/>

            </DockPanel>
            <ListBox AlternationCount="2"  DockPanel.Dock="Top" Margin="0,0,0,0" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding ReferenceCollection, ElementName=local:MainWindow}" TextSearch.TextPath="SearchString" x:Name="ReferenceList" HorizontalContentAlignment="Stretch" ScrollViewer.CanContentScroll="False" SnapsToDevicePixels="True" AllowDrop="True" BorderThickness="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
                <ListBox.Background>
                    <LinearGradientBrush StartPoint="1,1" EndPoint="1,0">
                        <GradientStop Offset="0.0" Color="#190000FF"/>
                        <GradientStop Color="#000000FF" Offset="1.0"/>
                    </LinearGradientBrush>
                </ListBox.Background>
                <ListBox.ItemTemplate>
                        <StaticResource ResourceKey="ListViewTemplate"/>
                </ListBox.ItemTemplate>
                <ListBox.ContextMenu>
                    <ContextMenu Style="{StaticResource ListBoxContextMenu}">
                        <MenuItem x:Name="EditContextMenuItem" Header="Edit" Click="EditListBoxItem" Style="{StaticResource ListBoxContextMenuItem}"/>
                        <MenuItem x:Name="DeleteContextMenuItem" Header="Delete" Click="DeleteListBoxItem" Style="{StaticResource ListBoxContextMenuItem}"/>
                        <MenuItem x:Name="NewContextMenuItem" Header="New" Click="NewListBoxItem" Style="{StaticResource ListBoxContextMenuItem}"/>
                    </ContextMenu>
                </ListBox.ContextMenu>
            </ListBox>
        </DockPanel>
    </Grid>
</Grid>
</UserControl>

AddReferencePage的代码隐藏：

Imports System.Collections.ObjectModel
Imports System.ComponentModel
Imports System.Collections.Specialized
Imports System.Windows.Threading
Imports System.Windows.Media.Animation
Imports System.Globalization

Public Class AddReferencePage
Private SelectImage As Boolean = False

Private Sub ReturnToReferences(sender As Object, e As RoutedEventArgs)
    Dim PW As MainWindow = Window.GetWindow(AddReferencePage)
    If PW IsNot Nothing Then
        If ReferenceAuthor.Text <> "Author" Or ReferenceDate.Text <> "Date" Or ReferenceTitle.Text <> "Title" Then
            Dim CN As String() = Nothing
            Dim FN As String = Nothing
            Dim LN As String = Nothing
            Dim YR As String = Nothing
            Dim TT As String = Nothing

            If ReferenceAuthor.Text = "Author" Then
                ReferenceAuthor.Text = "Unknown"
                FN = Nothing
                LN = "Unknown"
            Else
                If ReferenceAuthor.Text.Contains(" ") Then
                    CN = ReferenceAuthor.Text.Split(" ")
                    FN = CN.First
                    LN = CN.Last
                Else
                    FN = Nothing
                    LN = ReferenceAuthor.Text
                End If

            End If
            If ReferenceDate.Text = "Date" Then
                ReferenceDate.Text = "Unknown"
                YR = "Unknown"
            Else
                YR = ReferenceDate.Text
            End If
            If ReferenceTitle.Text = "Title" Then
                ReferenceTitle.Text = "Unknown"
                TT = "Unknown"
            Else
                TT = ReferenceTitle.Text
            End If
            If PW.NewItem = False Then
                PW.ReferenceCollection.Remove(PW.EditItem)
                PW.AddReferenceItem(FN, LN, TT, YR, "Book")
            Else
                PW.AddReferenceItem(FN, LN, TT, YR, "Book")
            End If
        End If
    End If
    PW.ChangeSlide(sender, 0)
End Sub

Private Sub ButtonsMouseEnter(sender As Button, e As RoutedEventArgs)
    Select Case sender.Name
        Case "ReturnReferences"
            sender.Content = FindResource("BackArrowHover")
    End Select
End Sub

Private Sub ButtonsMouseLeave(sender As Button, e As RoutedEventArgs)
    Select Case sender.Name
        Case "ReturnReferences"
            sender.Content = FindResource("BackArrowNormal")
    End Select
End Sub

Private Sub ButtonsMouseDown(sender As Button, e As RoutedEventArgs)
    Select Case sender.Name
        Case "ReturnReferences"
            sender.Content = FindResource("BackArrowClick")
    End Select
End Sub

Public Sub SaveReferenceSub(sender As Object, e As RoutedEventArgs)
    Dim PW As MainWindow = Window.GetWindow(AddReferencePage)
    Dim CN As String() = ReferenceAuthor.Text.Split(" ")
    Dim FN As String = CN.First()
    Dim LN As String = CN.Last()
    Dim YR As Integer = CInt(ReferenceDate.Text)
    Dim TT As String = ReferenceTitle.Text
    If PW.NewItem = False Then
        PW.ReferenceCollection.Remove(PW.EditItem)
        PW.AddReferenceItem(FN, LN, TT, YR, "Book")
    Else
        PW.AddReferenceItem(FN, LN, TT, YR, "Book")
    End If
End Sub

Private Sub ReferenceDetails()
    Dim PW As MainWindow = Window.GetWindow(AddReferencePage)
    If PW.NewItem = False Then
        ReferenceAuthor.Text = PW.EditItem.PropFirstName & " " & PW.EditItem.PropLastName
        ReferenceTitle.Text = PW.EditItem.PropTitle
        ReferenceDate.Text = PW.EditItem.PropYear.ToString
    End If
End Sub

Private Sub AddReferencePage_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
    ReferenceDetails()
End Sub

Private Sub FieldEnter(sender As TextBox, e As RoutedEventArgs)
    Select Case sender.Name
        Case "ReferenceAuthor"
            If sender.Text = "Author" Then
                sender.Clear()
            End If
        Case "ReferenceTitle"
            If sender.Text = "Title" Then
                sender.Clear()
            End If
        Case "ReferenceDate"
            If sender.Text = "Date" Then
                sender.Clear()
            End If
    End Select
End Sub

Private Sub FieldLeave(sender As TextBox, e As RoutedEventArgs)
    If sender.Text = "" Then
        Select Case sender.Name
            Case "ReferenceAuthor"
                sender.Text = "Author"
            Case "ReferenceTitle"
                sender.Text = "Title"
            Case "ReferenceDate"
                sender.Text = "Date"
        End Select
    End If
End Sub

Private Sub FieldChanged(sender As TextBox, e As RoutedEventArgs)
    If sender.Text <> "Author" And sender.Text <> "Date" And sender.Text <> "Title" Then
        sender.Foreground = Brushes.Black
    Else
        sender.Foreground = Brushes.Gray
    End If
End Sub

Private Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
    If SelectImage = False Then
        SelectImageBox.BeginStoryboard(DirectCast(Me.Resources("LeftToRight"), Storyboard))
        SelectImage = True
    Else
        SelectImageBox.BeginStoryboard(DirectCast(Me.Resources("RightToLeft"), Storyboard))
        SelectImage = False
    End If
End Sub

Private Sub SelectImageBox_LostFocus(sender As Object, e As RoutedEventArgs) Handles SelectImageBox.LostFocus
    'If SelectImage = True Then
    '    SelectImageBox.BeginStoryboard(DirectCast(Me.Resources("RightToLeft"), Storyboard))
    '    SelectImage = False
    'End If
End Sub
End Class

AddReferencePage的XAML：

<UserControl x:Class="AddReferencePage" x:Name="AddReferencePage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:local="clr-namespace:ARC"
         mc:Ignorable="d"
         VerticalAlignment="Stretch" SnapsToDevicePixels="True" HorizontalAlignment="Stretch" d:DesignWidth="400" d:DesignHeight="600">
<UserControl.Resources>
    <Storyboard x:Key="RightToLeft" 
                AccelerationRatio=".5"
                DecelerationRatio=".5">
        <DoubleAnimation Storyboard.TargetName="ReferenceInfo" Storyboard.TargetProperty="(Canvas.Left)" Duration="0:0:0.3" To="0"/>
        <DoubleAnimation Storyboard.TargetName="SelectImageBox" Storyboard.TargetProperty="Opacity" Duration="0:0:0.3" From="1.0" To="0.0"/>
    </Storyboard>

    <Storyboard x:Key="LeftToRight" 
                AccelerationRatio=".5"
                DecelerationRatio=".5">
        <DoubleAnimation Storyboard.TargetName="ReferenceInfo" Storyboard.TargetProperty="(Canvas.Left)" Duration="0:0:0.3" To="{Binding ActualWidth, ElementName=AnimInfo}"/>
        <DoubleAnimation Storyboard.TargetName="SelectImageBox" Storyboard.TargetProperty="Opacity" Duration="0:0:0.3" From="0.0" To="1.0"/>
    </Storyboard>
</UserControl.Resources>


<Grid Background="#FFF1F1F1">
    <Button Style="{DynamicResource NoChromeButton}" x:Name="ReturnReferences" Click="ReturnToReferences" MouseDown="ButtonsMouseDown" MouseEnter="ButtonsMouseEnter" MouseLeave="ButtonsMouseLeave" VerticalAlignment="Top" HorizontalAlignment="Left" Margin="5,5,0,0" Height="48" Width="48">
        <DynamicResource ResourceKey="BackArrowNormal"/>
    </Button>

    <TextBlock Text="Edit References" FontFamily="Segoe UI Light" FontSize="36" Margin="72,3,0,0" VerticalAlignment="Top" HorizontalAlignment="Stretch"/>
    <TextBlock x:Name="AnimInfo" FontFamily="Segoe UI Light" FontSize="36" Margin="72,3,60,0" VerticalAlignment="Top" HorizontalAlignment="Stretch"/>
    <ListView x:Name="SelectImageBox" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Margin="72,59,60,20" Background="Transparent" ScrollViewer.HorizontalScrollBarVisibility="Disabled" BorderThickness="0" Opacity="0">
        <ListView.ItemsPanel>
            <ItemsPanelTemplate>
                <WrapPanel Orientation="Horizontal" IsItemsHost="True"/>
            </ItemsPanelTemplate>
        </ListView.ItemsPanel>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
        <Button Style="{DynamicResource NoChromeButton}" Height="48" Width="48">
            <DynamicResource ResourceKey="Book"/>
        </Button>
    </ListView>
    <Canvas x:Name="InfoCanvas" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Margin="72,60,0,0" Opacity="1">
        <DockPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Margin="0,0,0,0" x:Name="ReferenceInfo" Canvas.Left="0" Canvas.Top="0" Width="{Binding ActualWidth, ElementName=InfoCanvas}" Height="{Binding ActualHeight, ElementName=InfoCanvas}">
            <TextBox x:Name="ReferenceAuthor" GotFocus="FieldEnter" TextChanged="FieldChanged" LostFocus="FieldLeave" FontSize="16" FontFamily="Segoe UI Light" Text="Author" Foreground="Gray" Background="Transparent" DockPanel.Dock="Top" VerticalAlignment="Top" HorizontalAlignment="Stretch" BorderThickness="0" Margin="0,2,0,2"/>
            <TextBox x:Name="ReferenceTitle" GotFocus="FieldEnter" TextChanged="FieldChanged" LostFocus="FieldLeave" FontSize="16" FontFamily="Segoe UI Light" Text="Title" Foreground="Gray" Background="Transparent" DockPanel.Dock="Top" VerticalAlignment="Top" HorizontalAlignment="Stretch" BorderThickness="0" Margin="0,2,0,2"/>
            <TextBox x:Name="ReferenceDate" GotFocus="FieldEnter" TextChanged="FieldChanged" LostFocus="FieldLeave" FontSize="16" FontFamily="Segoe UI Light" Text="Date" Foreground="Gray" Background="Transparent" DockPanel.Dock="Top" VerticalAlignment="Top" HorizontalAlignment="Stretch" BorderThickness="0" Margin="0,2,0,2"/>
        </DockPanel>
    </Canvas>
    <Button Style="{DynamicResource NoChromeButton}" Margin="5,60,0,0" VerticalAlignment="Top" HorizontalAlignment="Left" Width="48" Height="48" VerticalContentAlignment="Center" Click="Button_Click_1">
        <DynamicResource ResourceKey="Book"/>
    </Button>
</Grid>
</UserControl>

我知道很多代码：D但我真的需要解决这个问题！谢谢大家！如果您需要更多详细信息，请告诉我们。我的所有资源和模板都在Application.xaml中定义，由于不相关，我没有包含它。如果需要，我可以加入。

Answer 1

根据错误堆栈跟踪，错误发生在子ReferenceDetails()中，这是问题中倒数第二个代码块。我认为这些代码行中存在错误，

Dim PW As MainWindow = Window.GetWindow(AddReferencePage)
    If PW.NewItem = False Then

我没有使用WPF，只有Winforms。但如果设计师相似，那么MainWindow在设计时可能Nothing。您可以尝试这样的事情，看看它是否修复了错误。

Dim PW As MainWindow = Window.GetWindow(AddReferencePage)
    If PW IsNot Nothing AndAlso PW.NewItem = False Then

如果PW以Nothing的形式返回，则不会导致NullReferenceException。另外（我再次假设WPF设计人员的工作方式类似于Winfors），请确保在更改代码后重新构建，然后再尝试将其添加到主窗口。

Answer 2

感谢Kratz如此迅速地回应。经过一段时间的游戏，我发现我需要将用户控件放在一个Frame中。：d

由于UserControl，Designer中的NullReferenceException

2 个答案: