Hi Rajani Kulkarni,
In general, Telerik controls can be used in managed C++ applications. They are written in C#, but you can use them with VB and managed C++ as well. If you want to use Telerik controls at design time you need a managed C++ Winforms application.
They can be used in unmanaged environments too, for example, you may use ActiveX to create an application that uses Telerik WinForms controls in Internet Explorer. Please note that there are certain limitations when the controls are used as ActiveX components.
Please double check that you are creating a managed C++ application and reset your toolbox.
the Telerik team