Thank you for writing.
Currently the APIs that the Windows Phone environment provides offer little for keyboard interactivity. The only thing that a programmer can do to interact with the keyboard is to set the InputScope property of a text box. There are no notifications for keyboard shown or closed and there is no way to know if a keyboard is currently shown. Since there is no API RadMessageBox does not know how to hide the keyboard.
The only solution is to iterate over the whole Silverlight element tree on the current page, search for focused text box and remove the focus. We will consider implementing this in a future release. In the mean time I hope that manually removing the focus is acceptable.
Please write again if you have other feedback you would like to share.
All the best,
the Telerik team
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