The Upgrade Wizard for WPF cannot upgrade projects targeting the 4.8 .NET Framework.

1. Install the latest extension for WPF 
2. Create a new project targeting the 4.8 .NET Framework
3. Try to launch the Upgrade Wizard from the Telerik menu 
4. See the error - The project cannot be upgraded because the target framework does not match

In RadGanttView, the drag reorder visual element position indicators ('Before', 'After', and 'Inside') are not translated according to the application's UI culture settings (e.g., German), remaining displayed in English because they are hardcoded in the element's template.

To work this around, create a custom DragReorderTemplate and apply it via the CueTemplateSelector of GanttDragResizeVisualCue. This can be applied via an implicit style defined in App.xaml.

 <Style TargetType="telerik:GanttDragResizeVisualCue">
     <Setter Property="CueTemplateSelector">
         <Setter.Value>
             <telerik:GanttDragVisualCueContentTemplateSelector DragTemplate="{StaticResource GanttDragResizeVisualCueTemplate}"
                                                         ResizeTemplate="{StaticResource GanttDragResizeVisualCueTemplate}"
                                                         CreateDependencyTemplate="{StaticResource GanttCreateDependencyTemplate}"
                                                         DragReorderTemplate="{StaticResource CustomGanttDragReorderTemplate}" />
         </Setter.Value>
     </Setter>
 </Style>

The AM/PM value is not shown in the cell when formatting a time value.

Steps to reproduce:
1. Insert some time in a cell in spreadsheet (22:20)
2. Apply it a custom format that contains AM/PM (e.g. "h:mm AM/PM")

Observed: The AM/PM format is missing
Expected: AM or PM should be shown after the time (image attached) 

Declined: The changes could be applied if the user presses OK button instead of pressing Enter key. A new feedback item is open where the issue is described: https://feedback.telerik.com/Project/143/Feedback/Details/212042-spreadsheet-custom-number-type-values-in-format-cells-dialog-are-not-applied-wh

Workaround: Import the document without using the default command

OpenFileDialog openFileDialog = new OpenFileDialog();
openFileDialog.Filter = "All Spreadsheet Files (*.txt, *.csv, *.pdf, *.xlsx)|*.txt;*.csv;*.pdf;*.xlsx|Excel Workbook (*.xlsx)|*.xlsx|CSV (Comma delimited) (*.csv)|*.csv|Text (Tab delimited) (*.txt)|*.txt|All Files (*.*)|*.*";
if (openFileDialog.ShowDialog() == true)
{
    string extension = Path.GetExtension(openFileDialog.SafeFileName);
    using (Stream input = openFileDialog.OpenFile())
    {
        Workbook workbook = WorkbookFormatProvidersManager.Import(extension, input);
        workbook.Name = openFileDialog.SafeFileName; // in the default implementation this is set after applying the document to RadSpreadsheet and triggers the event
       
        this.radSpreadsheet.Workbook = workbook;
    }
}

When using RadChat control and running the application, 2 binding errors appear in the Output Tab of Visual Studio.

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Telerik.Windows.Controls.RadPromptInput', AncestorLevel='1''. BindingExpression:Path=Padding; DataItem=null; target element is 'RadGlyph' (Name=''); target property is 'Margin' (type 'Thickness')

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Telerik.Windows.Controls.RadPromptInput', AncestorLevel='1''. BindingExpression:Path=Padding; DataItem=null; target element is 'RadGlyph' (Name=''); target property is 'Margin' (type 'Thickness')

Environment:

• Visual Studio 2026 Version 18.6.1 (May 2026 release)
• Visual Studio language: Japanese
• .NET 10 WPF project
• Telerik UI for WPF 2026.2.520
  

Problem:

Visual Studio freezes frequently while editing XAML when using Telerik UI for WPF 2026.2.520.
The issue does NOT occur with Telerik UI for WPF 2026.1.415.

Steps to reproduce:

1. Install the "Progress Telerik UI for WPF Extension"
2. Create a new WPF project using the Telerik extension/template (Empty)
3. Open the automatically generated MainWindow.xaml
4. Inside the existing <Grid> element, type:
   <Grid
5. At the moment XAML IntelliSense/code completion is triggered, Visual Studio freezes

Additional information:

• XAML Designer is disabled
• Deleting the .vs folder does not help
• No third-party Visual Studio extensions are installed
• The issue only occurs with Telerik UI for WPF 2026.2.520
• Downgrading to Telerik UI for WPF 2026.1.415 resolves the issue completely
  

Could you please confirm whether this is a known issue related to Visual Studio 2026 / .NET 10 compatibility?

Steps to reproduce: 

1. Enter in a cell =Today()
2. Show Format Cells dialog and set Custom format "d"

Expected: The value is the day of the month.
Actual: The date is formatted as short date but has to be day of the month.

As a result, the glyphs are not measured and positioned properly. The issue applies to the TrueType and Type1 fonts.

The TableCellProperty.Padding property of the "TableNormal" StyleDefinition doesn't take effect in the UI. The same is valid for the TableProperties.CellPadding property.

To work this around, you can manually set the Padding property of all TableCell elements in the RadDocument.

 var cells = radDocument.EnumerateChildrenOfType<Telerik.Windows.Documents.Model.TableCell>();
 foreach (var cell in cells)
 {
     cell.Padding = new Padding(10);
 }

Hi Team,

We have a large-scale WPF application that uses the Telerik WPF RadGridView across multiple screens. We are experiencing significant memory growth issues. Upon deep analysis of the memory dump, we observed that the RadGridView continuously pushes DispatcherPriority items into the Dispatcher queue. We also noticed an internal timer within the RadGridView that appears to be active even after the control is no longer visible.  We would like to understand how to completely detach and stop this internal timer once the control is removed from the screen, and why the RadGridView keeps pushing DispatcherItem entries into the Dispatcher queue.

Telerik Version : 2017.2.503.45

Since the last update, we receive often the following exception from our users log. I don't know exactly how to reproduce, but I know that when it happens, the user tries to click anywhere in the document and each time the exception is thrown. The users need to close and reopen the document to make it work again.

System.NullReferenceException: Object reference not set to an instance of an object. at Telerik.Windows.Documents.UI.DocumentPresenterBase.CaretPosition_PositionChanged(Object sender, EventArgs e) at Telerik.Windows.Documents.DocumentPosition.MoveToPosition(DocumentPosition newPosition) at Telerik.Windows.Documents.Selection.MouseSelectionHandler.UpdateSelectionAndCaretPosition() at Telerik.Windows.Documents.Selection.MouseSelectionHandler.RegisterDocumentMouseMove(Point position, SourceType source) at Telerik.Windows.Documents.UI.DocumentPresenterBase.HandleMouseMoveOnPosition(Point position, SourceType source) at Telerik.Windows.Documents.UI.DocumentPresenterBase.Owner_MouseMove(Object sender, MouseEventArgs e) at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args) at System.Windows.Input.InputManager.ProcessStagingArea() at System.Windows.Input.MouseDevice.Synchronize() at System.Windows.Input.MouseDevice.PostProcessInput(Object sender, ProcessInputEventArgs e) at System.Windows.Input.InputManager.ProcessStagingArea() at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel) at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at System.Windows.Interop.HwndSource.InputFilterMessage(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 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

We also had this case when we try programatically to move the caret (seems to be the same end result exception):

System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Windows.Documents.UI.DocumentPresenterBase.CaretPosition_PositionChanged(Object sender, EventArgs e)
   at Telerik.Windows.Documents.DocumentPosition.MoveToDocumentStart()
   at Telerik.Windows.Documents.DocumentPosition.MoveToFirstPositionInDocument()