Unplanned
Last Updated: 23 Apr 2025 05:47 by Martin Ivanov
The initial selection doesn't work when RadComboBox is placed in a DataTemplate (examples: ContentControl.ContentTemplate, GridViewDataColumn.CellTemplate) and the SelectedValuePath property of the control is set in a Style DataTrigger. To reproduce this the Binding of the DataTrigger should use a converter.

To work this around avoid using a binding in a DataTrigger to set the SelectedValuePath. Set the property directly on the RadComboBox instance, or use another technique based on your requirements.
Unplanned
Last Updated: 21 Mar 2025 13:05 by Stenly
In a touch scenario, when there are RadComboBox instances one below the other, selecting an item from a RadComboBox opens the RadComboBox instance, which is below the selected item. 

This is present when there is a global Style that targets the native WPF ScrollViewer element, which sets its PanningMode property to Both

To work this around, set the TouchManager.TouchMode to HitTestHidden, in order to exclude the RadComboBox from the TouchManager's events propagation.
Unplanned
Last Updated: 19 Mar 2025 15:11 by Martin Ivanov

ArgumentOutOfRangeException occurs when the ItemsSource of RadComboBox gets reset. To recreate this the IsSelected property of RadComboBoxItem should be bound too and multiple selection should be allowed.

To work this around, you can disable the autiomation peers globally:

AutomationManager.AutomationMode = AutomationMode.Disabled;

Or you disable them only for the RadComboBox:

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

The stacktrace:

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#

Won't Fix
Last Updated: 20 May 2024 09:33 by ADMIN
When in the RadGridView details template on a touch device subsequent clicks are not registered.
Completed
Last Updated: 20 Jun 2023 06:04 by ADMIN
Release LIB 2023.2.619 (19 Jun 2023)
The drop-down popup is sometimes not closed when hosted in an ElementHost in a WinForms application.
Completed
Last Updated: 22 May 2023 08:27 by ADMIN
Release LIB 2023.1.522 (22 May 2023)

The items of the RadComboBox control flicker when scrolling and the Windows 11 theme is applied.

To work this around, a new Style with TargetType="RadComboBoxItem" could be created for the ItemContainerStyle property of RadComboBox. Then, set the BorderBrush and ThemeHelper.MouseOverBrush properties to "#F9F9F9".

xmlns:helpers="clr-namespace:Telerik.Windows.Controls.Theming.Helpers;assembly=Telerik.Windows.Controls"

<telerik:RadComboBox.ItemContainerStyle>
    <Style TargetType="telerik:RadComboBoxItem">
        <Setter Property="helpers:ThemeHelper.MouseOverBrush" Value="#F9F9F9" />
        <Setter Property="BorderBrush" Value="#F9F9F9"/>
    </Style>
</telerik:RadComboBox.ItemContainerStyle>

Completed
Last Updated: 17 Nov 2022 07:11 by ADMIN
Release LIB 2022.3.1121 (21 Nov 2022)

The selected items of the RadComboBox will not be displayed correctly if the ItemsSource is bound to a collection of enums that are converted via a custom EnumConverter.

Currently, you could work around this behavior by implementing a custom DataTemplate for the MultipleSelectionBoxTemplate property of RadComboBox:

<telerik:RadComboBox x:Name="comboBox"
                     AllowMultipleSelection="True">
    <telerik:RadComboBox.MultipleSelectionBoxTemplate>
        <DataTemplate>
            <ItemsControl ItemsSource="{Binding ElementName=comboBox, Path=SelectedItems}"
                          AlternationCount="{Binding RelativeSource={RelativeSource Self}, Path=Items.Count}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <StackPanel Orientation="Horizontal"/>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBlock x:Name="commaTextBlock" Text=", "/>
                            <TextBlock Text="{Binding}" HorizontalAlignment="Left"/>
                        </StackPanel>
                        <DataTemplate.Triggers>
                            <Trigger Property="ItemsControl.AlternationIndex" Value="0">
                                <Setter Property="Visibility" TargetName="commaTextBlock" Value="Collapsed" />
                            </Trigger>
                        </DataTemplate.Triggers>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </DataTemplate>
    </telerik:RadComboBox.MultipleSelectionBoxTemplate>
</telerik:RadComboBox>

Completed
Last Updated: 05 Nov 2021 09:04 by ADMIN
Release R3 2021 SP
While editing the XAML document, I'm experiencing weird behavior in VS2019. 

All examples apply when the Design editor is active together with XAML editor.

Example 1:

Selecting XAML with mouse stops when I start selecting the telerik:RadComboBox.

Example 2:

Copy Pasting bugs out, either the selection is empty or incorrect.

Example 3:

'Forcus' in Visual Studio is sometimes overtaken by the RadComboBox. 
Completed
Last Updated: 15 Sep 2021 15:20 by Arif
Release LIB 2021.2.816 (16 Aug 2021)

Steps to Create Problem using  EditableTextBoxTemplate_WPF sample project provided by Telerik:(modified project is zipped and attached just in case)

- Edit Example.xaml to add "AllowMultipleSelection="True":

            <telerik:RadComboBox  IsEditable="True" ItemsSource="{Binding Companies}" SelectAllTextEvent="None" FontFamily="Calibri" FontSize="14"
                                  DisplayMemberPath="Name" EditableTemplate="{StaticResource EditableComboBox}"
                                  Width="220" Height="50" DropDownWidth="*" x:Name="comboBox" Margin="5 10" AllowMultipleSelection="True"/>
        </StackPanel>

 

1) Run project 

2) Click drop down button to see list in the drop down

3) Type "Global" (at this point it should autocomplete "Global Corporation")

4) Without clicking on anything or Press space bar to continue typing (type space character)

5) Typed text will disappear leaving only space character behind - At this point, nothing is selected.

 

This does NOT happen if typed text before space does NOT match with any item from the list. 

This does NOT happen if AllowMultipleSelection set to false

This does NOT happen if dropdown is NOT open while typing.

 

Completed
Last Updated: 13 Aug 2021 12:44 by ADMIN
Release LIB 2021.2.816 (16 Aug 2021)

NullReferenceException appears when the multiple selection is enabled, items are selected and the Text property of the RadComboBox control becomes null.

To resolve this, you can override the OnTextChanged method of RadComboBox and replace the null value with an empty string.

public class CustomRadComboBox : RadComboBox
{
	protected override void OnTextChanged(string oldValue, string newValue)
	{
		if (string.IsNullOrEmpty(newValue))
		{
			newValue = string.Empty;
			Dispatcher.BeginInvoke(new Action(() =>
			{
					SelectedItems.Clear();
			}));
		}
		base.OnTextChanged(oldValue, newValue);
	}
}

Unplanned
Last Updated: 30 Jul 2021 00:53 by Kun

In this case, the control is bound to a collection of strings. The collection contains equal string values. ("h1","h2","h1"). When the first item is selected and afterward we select the last one, will not trigger the SelectionChanged event. This behavior could be improved.

 

Completed
Last Updated: 31 May 2021 08:03 by ADMIN
Release LIB 2020.1.127 (01/27/2020)
Typing characters with Korean IME does not highlight the matching items.
Completed
Last Updated: 15 Mar 2021 08:57 by ADMIN
Release LIB 2021.1.315 (15/03/2021)

According to the following article, when the UpdateSelectionOnLostFocus property is set to True and you enter a text that cannot update the selection, once the control loses the focus, the typed text should stay in the textbox. 
https://docs.telerik.com/devtools/wpf/controls/radcombobox/howto/perform-selection-only-lost-focus

However, this doesn't happen if an item is already selected. In this case, the searched text is cleared. If you do not have a selection, then the text stays on lost focus. 

To work this around, you can cache the value of the RadComboBox's Text property in the PreviewLostKeyboardFocus event handler and then restore it in the LostFocus event handler. 

private string textCache;
private void RadComboBox_PreviewLostKeyboardFocus(object sender, System.Windows.Input.KeyboardFocusChangedEventArgs e)
{
	this.textCache = this.comboBox.Text;
}
private void RadComboBox_LostFocus(object sender, RoutedEventArgs e)
{
	this.comboBox.Text = this.textCache;
}

Completed
Last Updated: 30 Nov 2020 05:58 by ADMIN
Release LIB 2020.3.1130 (11/30/2020)

The "{" character cannot be entered in the RadComboBox when the keyboard is German (Swiss).

As a wokaround, you can inherit the RadComboBox and override the HandleKeyDown method:

public class CustomRadComboBox : RadComboBox
    {
        protected override bool HandleKeyDown(Key systemKey, int platformKeyCode)
        {
            if(systemKey == Key.Oem5)
            {
                return false;
            }
            return base.HandleKeyDown(systemKey, platformKeyCode);
        }
    }

Completed
Last Updated: 30 Sep 2020 05:17 by ADMIN
Release LIB 2020.3.1005 (10/05/2020)

When the theme variation is changed in the VisualStudio2013 theme, the mouse over color is not updated. 

As a workaround, we can reset the Template of the RadComboBox. 

var template = this.comboBox.Template;
this.comboBox.Template = null;
this.comboBox.Template = template;

 

Completed
Last Updated: 24 Jan 2020 15:33 by ADMIN
Release LIB 2020.1.127
Currently setting the Margin through the TextBoxStyle is not respected, since the TextBox control has its Margin set locally. 
Completed
Last Updated: 10 Oct 2019 05:31 by ADMIN
Release LIB 2019.3.1007

When you start navigating through the ribbon via the keytips or the arrow keys, and you get to a RadRibbonComboBox, this opens its drop down which contains RadRibbonComboBoxItems. 

In this case the keyboard navigation (using the arrows) of the RadRibbonComboBox doesn't work. This happens because the ribbon navigation implementation interfere with the combobox navigation.

Completed
Last Updated: 24 Sep 2019 06:56 by ADMIN
Release LIB 2019.3.923
When using the Telerik RadComboBox, a NVDA is not able to read the data items inside the combo box when the control is collapsed.
Completed
Last Updated: 22 Jul 2019 11:18 by ADMIN
Release Lib 2019.2.722 (07/22/2019)
Created by: Martin Ivanov
Comments: 0
Category: ComboBox
Type: Bug Report
1

If the height of RadComboBox is set to a value smaller than 26px (in Office2013) then the content of the RadToggleButton presenting the selected content is clipped.

This was reproduced with the Office2013 theme.

To work this around set the MinHeight of the child RadToggleButton to the same MinHeight as RadComboBox.

private void RadComboBox_Loaded(object sender, RoutedEventArgs e)
{
    var comboBox = (RadComboBox)sender;
    var toggle = comboBox.FindChildByType<RadToggleButton>();
    toggle.MinHeight = comboBox.MinHeight;
}

 

Completed
Last Updated: 22 Jul 2019 07:00 by ADMIN
Release LIB 2019.2.722 (7/22/2019)
When typing in RadComboBox, the first character will stay English letter, then Chinese symbols will be shown.
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