Telerik UI for Winforms

Release History

UI for WinForms R1 2021 (version 2021.1.122)

January 22, 2021

What's New

  • Office2019Light theme - inspired by the latest MS Office application.
  • RadToastNotificationManager - a component that builds toast notifications on that notification system and expand it, making it easier to create and manage notifications.
  • RadPictureBox - control used to display images in different formats like PNG, JPEG, BMP, etc. It supports both raster and vector (SVG) images. RadPictureBox is an extended version of the standard System.Windows.Forms.PictureBox.
  • PdfProcessing’s Engine inside RadPdfViewer - RadPdfViewer is optimized to work together with RadPdfProcessing library model. The new model is used by default. However, the user can easily switch to the old model by using the UsePdfProcessingModel and UsePdfProcessingModelDefaultValue boolean properties.
  • Multiple Resources UI in RadScheduler’s Edit Dialog - EditAppointmentDialog now provides UI for selecting multiple resources per appointment.
  • FilteringTimePrecision for the GridViewDateTimeColumn - a new GridViewDateTimeColumn.FilteringTimePrecision property is introduced.
  • ExportCheckBoxes in TreeViewSpreadExport - TreeViewSpreadExport allows you to export the check box values, when they are shown in tree nodes.
  • Brand new set of SVG images for TelerikMetro theme.
  • Installing LIB from NuGet - Latest Internal Builds are available for installing as a NuGet package.

Known Issues

  • Projects fail to build in .NET Core/.NET 5.0 while restoring NuGet. The solution is to create the missing ToolboxNuGetPackages folder in the installation folder of the controls, usually at: C:\Program Files (x86)\Progress\ToolboxNuGetPackages. Only users that have Telerik installation will be affected.

Telerik Installation

  • Fixed an installation issue that occurred on some operating systems.


  • FileExplorer Control throws an exception.


  • Provides mechanism for clearing the validation errors. New ClearErrorStatus method.


  • Added accessibility to the control.


  • The connecting lines between data points and their labels are not positioned correctly in a Cartesian series if you zoom and pan.


  • LoadLayout gets slower and slower after clearing all the items.


  • RadListDataItem.Selected property is not serialized in the designer.


  • Bottom border line is not visible on 125%/150%/175% scaling.


  • Expose API notifying that the end user is changing the group sort order. New Events GroupSortChanging, GroupSortChanged.
  • Provide opportunity to filter by seconds in RadSimpleListFilterPopup.
  • Header checkbox shouldn't be toggled when the column or the entire grid is ReadOnly.


  • Save button always stores the file as PNG no matter the selected extension.


  • Typo in RadListViewElement.


  • RadMenuItem.SvgImage property does not work correclty.


  • Improve its API to provide handling of the keyboard input.
  • IndexOutOfRangeException in RadPopupContainerForm.OnKeyDown.


  • Designer crashed in .NET 5 Project when adding a tab.
  • The Command Tabs cannot be selected in the .NET Core3.1/.NET 5.0 Visual Studio designer.
  • The selected tab is not persisted in the Visual Studio designer.


  • Add possibility to assign multiple resources for a single appointment via the UI.
  • The last resource seems cut when the vertical scrollbar is displayed.
  • Appointments are placed in the wrong cell when the ActiveView.StartDate is changed.
  • Changing the scale to Weeks in the timeline view does not update the start date.


  • Add a public method to get CaretPosition by MouseEventArgs.Location.
  • Setting the AllowScaling property to false should also hide the zoom drop down.
  • Horizontal scrollbar is clipped when the zoom factor is set to less than 100%.


  • Provide option in TreeViewSpreadExport to export checkboxes and radio buttons.
  • Selecting Range causes selection to Root Element.


  • Add custom fonts in Html-like text formatting.
  • An exception is thrown when RadForm is used in COM object in Excel sheet: Can't find type converter from string to property of RadSvgImage type.

TPF Designtime Support

  • The ThemeNameEditor should only list themes added to the form.


  • Added support for Type 3 fonts.
  • Provide API that allows customizing or changing the signature dialogs.
  • One should click twice in order to edit a filed, flickering when editing fields.
  • Editor's font is too big in high DPI.
  • TextSearch fails to find results when searching for a text on separate lines.


  • Performance improvements when inserting tables using the RadFixedDocumentEditor.
  • An ArgumentException is thrown when importing a PDF containing overlapping codespace.
  • An ArgumentException is thrown when importing rectangle whose values are defined using indirect references.
  • An ArgumentOutOfRangeException is thrown when a TextBox field has a smaller size than the default padding of the field.
  • Importing a document containing link annotations and named destinations referring to the same object causes InvalidCastException.
  • An InvalidCastException is thrown when importing a document with FormXObject resources pointing to an indirect object.
  • An InvalidDataException is thrown while decoding stream from a PDF with Encryption Algorithm 4.
  • An InvalidDataException (Unknown compression method 'method-name') is thrown when opening a document.
  • An InvalidDataException is thrown when importing a document containing two trailers and the Encrypt object is part of the first Xref table.
  • Image with ICC Based colorspace is missing due to a NullReferenceException.
  • A NotSupportedException is thrown when the inline image stream starts on a new row.
  • Slow performance of CCITTFaxDecode filter.
  • Sporadical InvalidOperationException is thrown while importing documents from background threads.


  • Letters dissapear in Korean IME after upgrading to the latest version.
  • An exception is thrown when adding a space after a table is placed in the header or footer.
  • An ArgumentNullException is thrown when importing a document with a structured document tag with no prefix mapping in the data binding declaration.
  • Deleting permission range with backspace when you are at the end of the annotation leads to deletion of the text after that.
  • DocxFormatProvider cannot import the content of a document when the main document part is not named document.xml.
  • Importing structured document tags with auto-close SdtContent tag throws InvalidCastException exception.
  • Inserting a checkbox in an empty paragraph preceded by another empty one deletes the paragraph.
  • Paragraphs inherit alignment from the align attribute value of their parent table when importing from HTML.
  • RepeatingSection's title cannot be set through the properties dialog.
  • SetPosition() sets the caret position on a previous location in a specific setup.
  • Setting document position after an inline content control moves the position to the last position in the control. It should move it after the control instead.
  • The paragraphs in the table are inheriting the negative indent from the previous paragraph.
  • The wrapping of a floating image is not parsed and applied while reading a DOCX file.
  • Typing text after a highlighted span carries over the highlight setting to the new content.
  • XamlParseException is thrown in RadRichTextEditor(.NET Framework) when importing xaml document exported in RadRichTextEditor(.NET Core).


  • Introduced DocumentInfo properties to preserve document metadata information.
  • Introduced support for importing/exporting/editing of Content Controls (structured document tags).
  • LoadFromUri event is now obsolete. LoadStylesheetFromUri and LoadImageFromUri are the new events that should be used instead. When LoadFromUri is used for resolving images, even if the data is provided in the arguments, an HTTP call to the resource is made to resolve its extension. This can be potentially unwanted behavior in some client scenarios.
  • Introduced support for floating images when exporting to PDF.
  • Headings elements ('h1'-'h6') are imported from HTML with wrong styling.
  • Html style property values are omitted on import when the value contains a semicolon.
  • List indentation is imported from RTF as local paragraph properties.
  • A NullReferenceException is thrown while importing a document with header/footer and main part not named with the default name.
  • An OutOfMemoryException is thrown when exporting TabStops to PDF.
  • A paragraph in a TableCell which is in the last TableRow on the page is not exported to the PDF document.
  • Exporting documents to PDF creates a fully transparent polygon for text without predefined highlight and/or background color. As a result, the size of the exported PDF is improved by up to 40%.
  • Hyperlinks are not correctly exported to plain text.
  • Wrong NuGet dependencies cause a build-time error.
  • There is an empty space between two consecutive paragraphs with a defined background color when the SpacingBefore on the second is bigger than the SpacingAfter on the first.


  • Added DocumentInfo properties to preserve document metadata information.
  • An exception is thrown when importing an XLS file with a specific print area.
  • An InvalidOperationException is thrown when importing an XLS document containing an Extra Table Data record.

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