C# – How to debug binding in WPF

add-inc++debuggingexcelwpf

I have a VS2008, C# WPF, Excel AddIn; Under some case, My addin throws exception like

A first chance exception of type 'System.InvalidOperationException' occurred in PresentationFramework.dll
A first chance exception of type 'System.NullReferenceException' occurred in PresentationFramework.dll

but I could not locate where the exception comes from. I know it is b/c data binding. but unable to find out where. Each time I step in, VS tracks to a method which executes w/o error, then after that, the exception throws and but no clue of which line of code.

I have been struggling this for days and could not make a little progress.
Pls help out. thanks

Edit, it is too long to fit in comment. So I just put xaml file here. @xmal file that throws the exception. It is DataGridComboBoxColumn that throws the exception

<UserControl x:Class="View.BasketView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dg="http://schemas.microsoft.com/wpf/2008/toolkit" >
    <UserControl.Resources>
        <sharedC:FunctionToHiddenVisibility x:Key="enumSRToVis"/>
        <sharedC:FunctionToHiddenVisibility x:Key="enumCSToVis"/>
        <Style x:Key="DataGridRowStyle"  TargetType="{x:Type dg:DataGridRow}">
            <Style.Triggers>
                <Trigger Property="AlternationIndex" Value="1" >
                    <Setter Property="Background" Value="Beige" />
                </Trigger>
            </Style.Triggers>
            <Setter Property="AllowDrop" Value="True" />
            <Setter Property="Margin" Value="0 2 0 2" />            
        </Style>
        <Style x:Key="DataGridStyle" TargetType="{x:Type dg:DataGrid}">
            <Setter Property="AlternationCount" Value="2" />
            <Setter Property="RowStyle" Value="{StaticResource DataGridRowStyle}" />
        </Style>
        <Style TargetType="{x:Type MenuItem}">
            <Style.Triggers>
                <Trigger Property="MenuItem.IsHighlighted" Value="True" >
                    <Setter Property="BorderBrush" >
                        <Setter.Value>
                            <SolidColorBrush Color="Gray"></SolidColorBrush>
                        </Setter.Value>
                    </Setter>
                    <Setter Property="BorderThickness" Value="1"/>
                </Trigger>
            </Style.Triggers>
        </Style>        
    </UserControl.Resources>
    <GroupBox>
        <GroupBox.Header>
            <TextBlock FontSize="14" FontFamily="Verdana" Text="{Binding Header,Mode=OneWay}"></TextBlock>
        </GroupBox.Header>

        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="33"></RowDefinition>
                <RowDefinition Height="*" ></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
            </Grid.RowDefinitions>

            <Border Margin="2 2 2 0">
                <Grid>

                    <Menu Background="Transparent">
                        <Menu.Resources>
                            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
                        </Menu.Resources>
                        <MenuItem IsEnabled="{Binding IsItemSelected}" Click="EditClick" ToolTip="Edit Relation(s)" Background="Transparent">
                            <MenuItem.Header>
                                <Image Width="16" Height="16" Source="{Binding EditImageFilePath}"/>
                            </MenuItem.Header>
                        </MenuItem>
                        <MenuItem IsEnabled="{Binding IsItemSelected}" Click="DeleteClick" ToolTip="Delete Relation(s)" Background="Transparent">
                            <MenuItem.Header>
                                <Image Width="16" Height="16" Source="{Binding DeleteImageFilePath}"/>
                            </MenuItem.Header>
                        </MenuItem>
                    </Menu>                             
                </Grid>
            </Border>

            <dg:DataGrid Grid.Row="1" x:Name="basketDG" Margin="5 0 5 0" Background="White"
                  AutoGenerateColumns="False" 
                  Style="{StaticResource DataGridStyle}"
                  SelectionMode="Extended"
                  GridLinesVisibility="None"
                  HeadersVisibility="Column" RowDetailsVisibilityMode="VisibleWhenSelected"
                  ItemsSource="{Binding BasketItems, Mode=OneWay}" CanUserAddRows="False" CanUserDeleteRows="False"
                  SelectionUnit="FullRow" SelectedItem="{Binding SelectedRelComplete}" 
                  VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled"
                  SelectionChanged="BasketDgSelectionChanged"                  
                  Drop="DataGridDrop" 
                  DragEnter="DataGridDragEnter" 
                  AllowDrop="True"
                 >

                <!-- Column definition -->
                <dg:DataGrid.Columns>
                    <dg:DataGridTextColumn IsReadOnly="True" Width="100" Header="Symbol" Binding="{Binding Name}" >
                        <dg:DataGridTextColumn.ElementStyle>
                            <Style TargetType="{x:Type TextBlock}">
                                <Setter Property="TextWrapping" Value="Wrap" />
                            </Style>
                        </dg:DataGridTextColumn.ElementStyle>
                    </dg:DataGridTextColumn>              

                    <dg:DataGridTextColumn IsReadOnly="True" Width="*" Header="Symbol Description" Binding="{Binding Desc}" >
                        <dg:DataGridTextColumn.ElementStyle>
                            <Style TargetType="{x:Type TextBlock}">
                                <Setter Property="TextTrimming" Value="WordEllipsis" />
                            </Style>
                        </dg:DataGridTextColumn.ElementStyle>
                    </dg:DataGridTextColumn>

                    <dg:DataGridComboBoxColumn Width="200" Header="Column" 
                        SelectedValueBinding="{Binding Path=RelParams.ColumnName, UpdateSourceTrigger=PropertyChanged}"
                        DisplayMemberPath="cName"
                        SelectedValuePath="cName">
                        <dg:DataGridComboBoxColumn.ElementStyle>
                            <Style TargetType="ComboBox">
                                <Setter Property="ItemsSource" Value="{Binding RelInfo.Columns}" />
                            </Style>
                        </dg:DataGridComboBoxColumn.ElementStyle>
                        <dg:DataGridComboBoxColumn.EditingElementStyle>
                            <Style TargetType="ComboBox">
                                <Setter Property="ItemsSource" Value="{Binding RelInfo.Columns}" />
                            </Style>
                        </dg:DataGridComboBoxColumn.EditingElementStyle>
                    </dg:DataGridComboBoxColumn>

                </dg:DataGrid.Columns>               

            </dg:DataGrid>

            <Grid Grid.Row="2" Margin="0 5 0 0">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" ></ColumnDefinition>
                    <ColumnDefinition Width="Auto" ></ColumnDefinition>
                    <ColumnDefinition Width="5" ></ColumnDefinition>
                    <ColumnDefinition Width="Auto" ></ColumnDefinition>
                </Grid.ColumnDefinitions>
                <StackPanel HorizontalAlignment="Left" Orientation="Horizontal" Grid.Column="0">
                    <Button Name="BtnSR" Visibility="{Binding SelectedFunction,  Converter={StaticResource enumSRToVis}}" IsEnabled="{Binding ItemsExist}" Margin="2" Click="ShowBasketSettings">Basket Settings</Button>
                </StackPanel>
                <StackPanel HorizontalAlignment="Left" Orientation="Horizontal" Grid.Column="0">
                    <Button Name="BtnCS" Visibility="{Binding SelectedFunction,  Converter={StaticResource enumCSToVis}}" IsEnabled="{Binding OnlyOneFutureItemExist}" Margin="2" Click="ShowCreateCurve">Curve Settings</Button>
                </StackPanel>
                <StackPanel Grid.Column="1">
                    <Button Width="50" Name ="BtnClear" ToolTip="Clear Basket" Margin="2" IsEnabled="{Binding ItemsExist}"
                            Click="BtnClear_Click">Clear</Button>
                </StackPanel>
                <StackPanel HorizontalAlignment="Right" Orientation="Horizontal" Grid.Column="3">                 
                    <Button Visibility ="{Binding ElementName=BtnSR, Path=Visibility}" 
                            ToolTip="Send Series Data to Table"
                            Name="SendToTable" Margin="2" Command="{Binding SendToTableCommand}" 
                            CommandParameter="{Binding ElementName=SendToTable}">Send to Table</Button>
                </StackPanel>
                <StackPanel HorizontalAlignment="Right" Orientation="Horizontal" Grid.Column="3">
                    <Button Visibility="{Binding ElementName=BtnCS, Path=Visibility}" 
                            Name="CreateCurveSurface" Margin="2"                             
                            ToolTip="Send Curve Surface to Table"
                            IsEnabled="{Binding OnlyOneFutureItemExist}"
                            Click="CreateCurveSurfaceClick"
                    >Send to Table</Button>
                </StackPanel>
            </Grid>
        </Grid>
    </GroupBox>
</UserControl>

Edit: here is stack trace

Name:NullReferenceException Message:Object reference not set to an
instance of an object. Target:Void
RestoreAttachedItemValue(System.Windows.DependencyObject,
System.Windows.DependencyProperty) Stack: at
Microsoft.Windows.Controls.DataGridRow.RestoreAttachedItemValue(DependencyObject
objectWithProperty, DependencyProperty property) at
Microsoft.Windows.Controls.DataGridRow.SyncProperties(Boolean
forcePrepareCells) at
Microsoft.Windows.Controls.DataGridRow.PrepareRow(Object item,
DataGrid owningDataGrid) at
Microsoft.Windows.Controls.DataGrid.PrepareContainerForItemOverride(DependencyObject
element, Object item) at
System.Windows.Controls.ItemsControl.MS.Internal.Controls.IGeneratorHost.PrepareItemContainer(DependencyObject
container, Object item) at
System.Windows.Controls.ItemContainerGenerator.System.Windows.Controls.Primitives.IItemContainerGenerator.PrepareItemContainer(DependencyObject
container) at
System.Windows.Controls.VirtualizingStackPanel.InsertContainer(Int32
childIndex, UIElement container, Boolean isRecycled) at
System.Windows.Controls.VirtualizingStackPanel.AddContainerFromGenerator(Int32
childIndex, UIElement child, Boolean newlyRealized) at
System.Windows.Controls.VirtualizingStackPanel.BringIndexIntoView(Int32
index) at
Microsoft.Windows.Controls.DataGrid.ScrollRowIntoView(Object item)
at Microsoft.Windows.Controls.DataGrid.OnScrollIntoView(Object arg)
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) at
System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback,
Object args, Int32 numArgs, Delegate catchHandler) at
System.Windows.Threading.DispatcherOperation.InvokeImpl() at
System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object
state) at System.Threading.ExecutionContext.runTryCode(Object
userData) at
System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode
code, CleanupCode backoutCode, Object userData) at
System.Threading.ExecutionContext.RunInternal(ExecutionContext
executionContext, ContextCallback callback, Object state) at
System.Threading.ExecutionContext.Run(ExecutionContext
executionContext, ContextCallback callback, Object state, Boolean
ignoreSyncCtx) 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
MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object
source, Delegate method, Object args, Int32 numArgs, Delegate
catchHandler) at
System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback,
Object args, Int32 numArgs, Delegate catchHandler) at
System.Windows.Threading.Dispatcher.InvokeImpl(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.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Window.ShowHelper(Object booleanBox) at
System.Windows.Window.Show() at System.Windows.Window.ShowDialog()

Best Solution

I am not sure about the cause of your problem but here are some links on How you can debug the WPF bindings -

How can I debug WPF bindings? http://www.zagstudio.com/blog/486 (WayBackLink)

Debugging Data Bindings in a WPF or Silverlight Application http://blogs.msdn.com/b/wpfsldesigner/archive/2010/06/30/debugging-data-bindings-in-a-wpf-or-silverlight-application.aspx (WayBackLink)

WPF Snippet - Detecting Binding Errors
http://www.switchonthecode.com/tutorials/wpf-snippet-detecting-binding-errors (WayBackLink)

Debug Databinding Issues in WPF
http://www.wpftutorial.net/DebugDataBinding.html

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