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2021 Releases

This article lists the breaking or important changes in the 2021 releases of Kendo UI.

Telerik UI for ASP.NET Core R3 2021 SP1


As of the 2021 R3 SP1 release, the ColorPicker has a new design and some new features were introduced. The .ClearButton() configuration is substituted with .CleatOnSelect(). In addition, if you desire to revert to the legacy design use the following configuration:

        .Views(new string[] { "gradient"})

Telerik UI for ASP.NET Core R3 2021

Important change

SASS Bootstrap Theme

As of the 2021 R3 release the Bootstrap SASS theme targets Bootstrap 5. Support for form-* classes has been dropped.

Telerik UI for ASP.NET Core R2 2021

Important change


As of the 2021 R2 release the events that are 24 hours or longer and do not have their isAllDay field set to true will be rendered in the regular (non all day) slots. In the previous versions such events were rendered in the allDaySlot. With the introduced change the allDaySlot will display only those events that have their isAllDay field set to true.

Telerik UI for ASP.NET Core R1 2021


Changes appear in the Grid Toolbar which now utilizes the CSS flexbox concept. This change improves Grid Toolbar responsiveness and visualization on smaller screen sizes.

Reverting to the previous appearance is possible by:

  • setting the Search Panel as the last element in the toolbar
.ToolBar(toolbar =>
  • utilizing the following styles:
     .k-grid .k-grid-search {
            margin-left: auto;
            margin-right: 0;


In previous versions, when setting the Height option, the total height of the Window was equal to the specified value plus the title bar height. As of 2021 R1, the Window now sets the height by also taking into account the title bar height and including it in the calculation. Thus, if height is specified to 200 pixels, this means that the full Window height will be 200 pixels. This change improves the Window behavior and allows for correctly specifying the height of the Window in percentage.

This change will affect Window instances that have height specified explicitly (height will be reduced with the title bar height). Reverting to the previous state is possible by increasing the height accordingly:

    .Height(250) // increase this value with the title bar height
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