var processing_provider = new Telerik.Windows.Documents.Flow.FormatProviders.Docx.DocxFormatProvider();

var document = processing_provider.Import(File.ReadAllBytes("C:\\Users\\test\\Downloads\\word1.docx"),null);
var bytes_ = processing_provider.Export(document, null);

var rtb_provider = new Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.DocxFormatProvider();
var doc = rtb_provider.Import(bytes_);
radRichTextBox.Document = doc;

public MainWindow()
{
    InitializeComponent();
    this.radExpander.SetBinding(RadExpander.IsExpandedProperty, new Binding("IsExpanded"));
}

<Style TargetType="telerik:RadRibbonWindow" BasedOn="{StaticResource RadRibbonWindowStyle}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="telerik:RadRibbonWindow">
                <Border x:Name="outerBorder" Background="{TemplateBinding WindowBackground}" CornerRadius="{TemplateBinding CornerRadius}">
                    <Grid x:Name="MaximizeWindowDecorator">
                        <Grid telerik:CornerRadiusHelper.ClipRadius="{Binding ElementName=outerBorder, Path=CornerRadius}" telerik:CornerRadiusHelper.ClipRadiusOffset="{TemplateBinding telerik:CornerRadiusHelper.ClipRadiusOffset}" Margin="{TemplateBinding BorderThickness}">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="28"/>
                                <RowDefinition Height="*"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto"/>
                                <ColumnDefinition Width="*"/>
                                <ColumnDefinition Width="Auto"/>
                            </Grid.ColumnDefinitions>
                            <Border Grid.Row="0" Grid.Column="1" Background="{telerik:Office2019Resource ResourceKey=HeaderBackgroundBrush}"/>
                            <Grid Grid.ColumnSpan="3">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="*"/>
                                </Grid.ColumnDefinitions>
                                <StackPanel x:Name="IconPanel" Orientation="Horizontal" HorizontalAlignment="Left" Visibility="{TemplateBinding IconVisibility}" VerticalAlignment="Center" Margin="4 0 0 0">
                                    <Image
                                    Name="PART_Icon"
                                    shell:WindowChrome.IsHitTestVisibleInChrome="True"
                                    Source="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Icon, Converter={StaticResource IconConverter}}"
                                    Width="{Binding Path=SmallIconSize.Width, Source={x:Static shell:SystemParameters2.Current}}"
                                    Height="{Binding Path=SmallIconSize.Height, Source={x:Static shell:SystemParameters2.Current}}"/>
                                    <Rectangle Width="1" Margin="4 0" Fill="{telerik:Office2019Resource ResourceKey=MainBorderBrush}"/>
                                </StackPanel>
                                <telerikRibbonViewPrimitives:WindowTitle x:Name="WindowTitle"
                                Grid.Column="1"
                                Title="{TemplateBinding Title}"
                                Style="{TemplateBinding TitleBarStyle}"
                                VerticalAlignment="Center"
                                HorizontalAlignment="Center"
                                Margin="0 0 65 0"/>
                            </Grid>
                            <StackPanel x:Name="buttonPanel" Orientation="Horizontal" Grid.ColumnSpan="3" HorizontalAlignment="Right" VerticalAlignment="Center" Margin="0 0 2 0">
                                <telerik:RadButton x:Name="minimizeButton"
                                                   shell:WindowChrome.IsHitTestVisibleInChrome="True"
                                                   ToolTipService.ToolTip="Minimize"
                                                   Command="{x:Static shell:SystemCommands.MinimizeWindowCommand}"
                                                   Style="{StaticResource RibbonWindowButtonStyle}"
                                                   CornerRadius="{Binding Path=CornerRadius.TopRight, RelativeSource={RelativeSource TemplatedParent}}">
                                    <telerik:RadButton.ToolTip>
                                        <TextBlock Text="{telerik:LocalizableResource Key=RibbonWindowMinimize}"/>
                                    </telerik:RadButton.ToolTip>
                                    <telerik:RadGlyph Glyph="{StaticResource GlyphMinimize}"/>
                                </telerik:RadButton>
                                <telerik:RadToggleButton x:Name="maximizeButton"
                                                         shell:WindowChrome.IsHitTestVisibleInChrome="True"
                                                         IsChecked="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=WindowState, Converter={StaticResource BooleanToWindowStateConverter}, Mode=TwoWay}"
                                                         Style="{StaticResource RadRibbonWindowToggleButtonStyle}"
                                                         CornerRadius="{Binding Path=CornerRadius.TopRight, RelativeSource={RelativeSource TemplatedParent}}">
                                    <telerik:RadGlyph Glyph="{StaticResource GlyphWindow}"/>
                                </telerik:RadToggleButton>
                                <telerik:RadButton x:Name="closeButton"
                                                   shell:WindowChrome.IsHitTestVisibleInChrome="True"
                                                   Command="{x:Static shell:SystemCommands.CloseWindowCommand}"
                                                   Style="{StaticResource RibbonWindowButtonStyle}"
                                                   CornerRadius="{Binding Path=CornerRadius.TopRight, RelativeSource={RelativeSource TemplatedParent}}">
                                    <telerik:RadButton.ToolTip>
                                        <TextBlock Text="{telerik:LocalizableResource Key=RibbonWindowClose}"/>
                                    </telerik:RadButton.ToolTip>
                                    <telerik:RadGlyph Glyph="{StaticResource GlyphClose}"/>
                                </telerik:RadButton>
                            </StackPanel>
                            <Border x:Name="PART_ClientAreaBorder" Grid.Column="1" Grid.Row="1" Margin="0 12 0 0" Background="{TemplateBinding Background}"/>
                            <AdornerDecorator x:Name="Adorner" Grid.Column="1" Grid.RowSpan="2">
                                <ContentPresenter Canvas.ZIndex="0" Name="PART_RootContentPresenter"/>
                            </AdornerDecorator>
                            <ResizeGrip x:Name="WindowResizeGrip"
                            Grid.Row="1"
                            Grid.Column="1"
                            shell:WindowChrome.ResizeGripDirection="BottomRight"
                            HorizontalAlignment="Right"
                            VerticalAlignment="Bottom"
                            Visibility="Collapsed"
                            IsTabStop="False"/>
                        </Grid>
                        <Border Background="{x:Null}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="{TemplateBinding CornerRadius}"/>
                    </Grid>
                </Border>
                <ControlTemplate.Triggers>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="Window.ResizeMode" Value="CanResizeWithGrip"/>
                            <Condition Property="Window.WindowState" Value="Normal"/>
                        </MultiTrigger.Conditions>
                        <Setter TargetName="WindowResizeGrip" Property="Visibility" Value="Visible"/>
                    </MultiTrigger>
                    <Trigger Property="Window.ResizeMode" Value="NoResize">
                        <Setter TargetName="minimizeButton" Property="Visibility" Value="Collapsed"/>
                        <Setter TargetName="maximizeButton" Property="Visibility" Value="Collapsed"/>
                    </Trigger>
                    <Trigger Property="Window.ResizeMode" Value="CanMinimize">
                        <Setter TargetName="maximizeButton" Property="IsEnabled" Value="False"/>
                    </Trigger>
                    <Trigger Property="WindowState" Value="Maximized">
                        <Setter TargetName="MaximizeWindowDecorator" Property="Margin" Value="6"/>
                        <Setter TargetName="maximizeButton" Property="Content">
                            <Setter.Value>
                                <telerik:RadGlyph Glyph="{StaticResource GlyphWindowCollapse}"/>
                            </Setter.Value>
                        </Setter>
                        <Setter Property="CornerRadius" Value="0"/>
                    </Trigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="telerik:RadRibbonWindow.IsAutoHideTaskbar" Value="true"/>
                            <Condition Property="Window.WindowState" Value="Maximized"/>
                        </MultiTrigger.Conditions>
                        <Setter TargetName="MaximizeWindowDecorator" Property="Margin" Value="-7 -2 -7 -6"/>
                    </MultiTrigger>
                    <Trigger Property="IsTitleVisible" Value="False">
                        <Setter TargetName="WindowTitle" Property="Visibility" Value="Collapsed"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

AutomationManager.AutomationMode = AutomationMode.Disabled;

public class CustomComboBox : RadComboBox
{
    protected override AutomationPeer OnCreateAutomationPeer()
    {
        return null;
    }
}

System.ArgumentOutOfRangeException: 'Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')'
  System.Private.CoreLib.dll!System.ThrowHelper.ThrowArgumentOutOfRange_IndexMustBeLessException() Unknown
  System.Private.CoreLib.dll!System.Collections.Generic.List<System.__Canon>.this[int].get(int index) Unknown  Telerik.Windows.Controls.Input.dll!Telerik.Windows.Automation.Peers.RadComboBoxAutomationPeer.RaiseSelectionEvents(System.Windows.Controls.SelectionChangedEventArgs e) Line 202 C#  Telerik.Windows.Controls.Input.dll!Telerik.Windows.Controls.RadComboBox.OnSelectionChanged(System.Windows.Controls.SelectionChangedEventArgs e) Line 1927 C#
  PresentationFramework.dll!System.Windows.Controls.Primitives.Selector.SetSelectedHelper(object item, System.Windows.FrameworkElement UI, bool selected) Unknown
  PresentationFramework.dll!System.Windows.Controls.Primitives.Selector.NotifyIsSelectedChanged(System.Windows.FrameworkElement container, bool selected, System.Windows.RoutedEventArgs e) Unknown
  PresentationCore.dll!System.Windows.EventRoute.InvokeHandlersImpl(object source, System.Windows.RoutedEventArgs args, bool reRaised) Unknown
  PresentationCore.dll!System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject sender, System.Windows.RoutedEventArgs args) Unknown
  Telerik.Windows.Controls.Input.dll!Telerik.Windows.Controls.RadComboBoxItem.OnSelected(System.Windows.RoutedEventArgs e) Line 59 C#
  PresentationFramework.dll!System.Windows.Controls.ListBoxItem.OnIsSelectedChanged(System.Windows.DependencyObject d, System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.NotifyPropertyChange(System.Windows.DependencyPropertyChangedEventArgs args) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.EntryIndex entryIndex, System.Windows.DependencyProperty dp, System.Windows.PropertyMetadata metadata, System.Windows.EffectiveValueEntry oldEntry, ref System.Windows.EffectiveValueEntry newEntry, bool coerceWithDeferredReference, bool coerceWithCurrentValue, System.Windows.OperationType operationType) Unknown
  PresentationFramework.dll!System.Windows.StyleHelper.ApplyStyleOrTemplateValue(MS.Internal.FrameworkObject fo, System.Windows.DependencyProperty dp) Unknown
  PresentationFramework.dll!System.Windows.StyleHelper.InvalidateContainerDependents(System.Windows.DependencyObject container, ref MS.Utility.FrugalStructList<System.Windows.ContainerDependent> exclusionContainerDependents, ref MS.Utility.FrugalStructList<System.Windows.ContainerDependent> oldContainerDependents, ref MS.Utility.FrugalStructList<System.Windows.ContainerDependent> newContainerDependents) Unknown
  PresentationFramework.dll!System.Windows.StyleHelper.DoStyleInvalidations(System.Windows.FrameworkElement fe, System.Windows.FrameworkContentElement fce, System.Windows.Style oldStyle, System.Windows.Style newStyle) Unknown
  PresentationFramework.dll!System.Windows.StyleHelper.UpdateStyleCache(System.Windows.FrameworkElement fe, System.Windows.FrameworkContentElement fce, System.Windows.Style oldStyle, System.Windows.Style newStyle, ref System.Windows.Style styleCache) Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.OnStyleChanged(System.Windows.DependencyObject d, System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.NotifyPropertyChange(System.Windows.DependencyPropertyChangedEventArgs args) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.EntryIndex entryIndex, System.Windows.DependencyProperty dp, System.Windows.PropertyMetadata metadata, System.Windows.EffectiveValueEntry oldEntry, ref System.Windows.EffectiveValueEntry newEntry, bool coerceWithDeferredReference, bool coerceWithCurrentValue, System.Windows.OperationType operationType) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.InvalidateProperty(System.Windows.DependencyProperty dp, bool preserveCurrentValue) Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.UpdateStyleProperty() Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.OnInitialized(System.EventArgs e) Unknown
  Telerik.Windows.Controls.Input.dll!Telerik.Windows.Controls.RadComboBoxItem.OnInitialized(System.EventArgs e) Line 106 C#
  PresentationFramework.dll!System.Windows.FrameworkElement.OnVisualParentChanged(System.Windows.DependencyObject oldParent) Unknown
  PresentationFramework.dll!System.Windows.Controls.ListBoxItem.OnVisualParentChanged(System.Windows.DependencyObject oldParent) Unknown
  PresentationCore.dll!System.Windows.Media.Visual.FireOnVisualParentChanged(System.Windows.DependencyObject oldParent) Unknown
  PresentationCore.dll!System.Windows.Media.Visual.AddVisualChild(System.Windows.Media.Visual child) Unknown
  PresentationCore.dll!System.Windows.Media.VisualCollection.Add(System.Windows.Media.Visual visual) Unknown
  PresentationFramework.dll!System.Windows.Controls.UIElementCollection.AddInternal(System.Windows.UIElement element) Unknown
  PresentationFramework.dll!System.Windows.Controls.Panel.GenerateChildren() Unknown
  PresentationFramework.dll!System.Windows.Controls.Panel.OnItemsChangedInternal(object sender, System.Windows.Controls.Primitives.ItemsChangedEventArgs args) Unknown
  PresentationFramework.dll!System.Windows.Controls.Panel.OnItemsChanged(object sender, System.Windows.Controls.Primitives.ItemsChangedEventArgs args) Unknown
  PresentationFramework.dll!System.Windows.Controls.ItemContainerGenerator.OnRefresh() Unknown
  PresentationFramework.dll!System.Windows.Controls.ItemContainerGenerator.OnCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args) Unknown
  WindowsBase.dll!System.Windows.WeakEventManager.ListenerList<System.Collections.Specialized.NotifyCollectionChangedEventArgs>.DeliverEvent(object sender, System.EventArgs e, System.Type managerType) Unknown
  WindowsBase.dll!System.Windows.WeakEventManager.DeliverEvent(object sender, System.EventArgs args) Unknown
  PresentationFramework.dll!System.Windows.Data.CollectionView.OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs args) Unknown
  WindowsBase.dll!System.Windows.WeakEventManager.ListenerList<System.Collections.Specialized.NotifyCollectionChangedEventArgs>.DeliverEvent(object sender, System.EventArgs e, System.Type managerType) Unknown
  WindowsBase.dll!System.Windows.WeakEventManager.DeliverEvent(object sender, System.EventArgs args) Unknown
  PresentationFramework.dll!System.Windows.Data.CollectionView.OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs args) Unknown
  PresentationFramework.dll!System.Windows.Data.ListCollectionView.RefreshOverride() Unknown
  PresentationFramework.dll!System.Windows.Data.CollectionView.RefreshInternal() Unknown
  PresentationFramework.dll!System.Windows.Data.CollectionView.DeferHelper.Dispose() Unknown
  PresentationFramework.dll!System.Windows.Controls.ItemCollection.SetCollectionView(System.Windows.Data.CollectionView view) Unknown
  PresentationFramework.dll!System.Windows.Controls.ItemsControl.OnItemsSourceChanged(System.Windows.DependencyObject d, System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  PresentationFramework.dll!System.Windows.FrameworkElement.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs e) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.NotifyPropertyChange(System.Windows.DependencyPropertyChangedEventArgs args) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.EntryIndex entryIndex, System.Windows.DependencyProperty dp, System.Windows.PropertyMetadata metadata, System.Windows.EffectiveValueEntry oldEntry, ref System.Windows.EffectiveValueEntry newEntry, bool coerceWithDeferredReference, bool coerceWithCurrentValue, System.Windows.OperationType operationType) Unknown
  WindowsBase.dll!System.Windows.DependencyObject.InvalidateProperty(System.Windows.DependencyProperty dp, bool preserveCurrentValue) Unknown
  PresentationFramework.dll!System.Windows.Data.BindingExpression.TransferValue(object newValue, bool isASubPropertyChange) Unknown
  PresentationFramework.dll!MS.Internal.Data.PropertyPathWorker.UpdateSourceValueState(int k, System.ComponentModel.ICollectionView collectionView, object newValue, bool isASubPropertyChange) Unknown
  PresentationFramework.dll!MS.Internal.Data.ClrBindingWorker.OnSourcePropertyChanged(object o, string propName) Unknown
  WindowsBase.dll!System.Windows.WeakEventManager.ListenerList<System.ComponentModel.PropertyChangedEventArgs>.DeliverEvent(object sender, System.EventArgs e, System.Type managerType) Unknown
  WindowsBase.dll!System.ComponentModel.PropertyChangedEventManager.OnPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs args) Unknown
  Telerik.Windows.Controls.dll!Telerik.Windows.Controls.ViewModelBase.OnPropertyChanged(string propertyName) Unknown
> WpfApp180.dll!WpfApp180.MainViewModel.ResetData() Line 44 C#

radGridView.ItemsSource = sampleData;
manager.AllowGridViewControls();

manager.AllowedTypes.Add(typeof(GridViewToggleRowDetailsColumn));
manager.AllowedTypes.Add(typeof(GridViewDataColumn));
manager.AllowedTypes.Add(typeof(DependencyObject));
manager.AllowedTypes.Add(typeof(Size));
manager.AllowedTypes.Add(typeof(SizeConverter));

var gridViewColumnType = typeof(Telerik.Windows.Controls.GridViewColumn);
var assembly = gridViewColumnType.Assembly;

// Get the internal type by its full name
var internalType = assembly.GetType("Telerik.Windows.Controls.GridViewColumnCollectionInternal", throwOnError: false);

// Use the type as needed (for example, add to AllowedTypes if required)
if (internalType != null)
{
    manager.AllowedTypes.Add(internalType);
}

public MyWpfUserControl()
{
    TelerikLicensing.Register("your-script-key");
    InitializeComponent();
}

public class CustomGridView: RadGridView
{
    private static readonly PropertyInfo internalColumnsProp = typeof(GridViewDataControl).GetProperty("InternalColumns", BindingFlags.Instance | BindingFlags.NonPublic);
    private static MethodInfo invalidateColumnsMethod;

    protected override Size MeasureOverride(Size availableSize)
    {
        if (EnableRowVirtualization && !double.IsInfinity(availableSize.Height))
        {
            var internalColumns = internalColumnsProp.GetValue(this);
            if (invalidateColumnsMethod == null)
            {
                invalidateColumnsMethod = internalColumns.GetType().GetMethod("InvalidateColumnWidthsCalculation", BindingFlags.Instance | BindingFlags.NonPublic);                     
            }

            invalidateColumnsMethod.Invoke(internalColumns, null);
        }
        return base.MeasureOverride(availableSize);
    }