RadVirtualKeyboard starts a new Task which constantly checks the system culture and synchronizes this with the culture of the control. When the control gets unloaded or when the SynchronizeCultureWithSystem property is set to False, the Task's thread is stopped using the Cancel method of the associated CancellationToken, along with the ThrowIfCancellationRequested method. 

This throws an OperationCanceledException, which is the expected behavior to signal that the thread was canceled. However, the exception is marked as unobserved, which throws the TaskScheduler.UnobservedTaskException static event. This doesn't cause problems in the control or the host application, but the RadVirtualKeyboard can handled it better, so the exception is not marked as unobserved.

Currently, when setting the Culture property of the RadVirtualKeyboard control, the OS keyboard layout will be changed as well.

We can add an option to control this behavior.

Add a property that allows you to set a Style targeting the key button elements. The property should work in the default scenario where the RadVirtualKeyboard control uses its default VirtualKeyboardTemplateSelector. If the selector is replaced, thus the DataTemplates with the buttons, the new property should not be applied.

Add an event on the RadVirtualKeyboard class that is raised when a key button is pressed. For example, KeyPressed or something like this. 

Hook to external keyboard special keys degrades performance the control so it might be useful to provide an API to disable this functionality.

On English keyboard the AltGr key is treated as Right Alt key which behaves the same as the standard (Left) Alt key. However, on some cultures (like French) the AltGr key is used as a modifier that toggles few special keys. This behavior is similar to holding the Shift key, but the set of special keys that are activated is different.

Currently, RadVirtualKeyboard doesn't support the special behavior of the AltGr key.