RadCalendar supports selection of whole weeks by the help of row headers. For additional information, please refer to this help article: Column and Row Headers.
If you want to select a whole week without the help of headers, but just by clicking on a date, you are free to make your own implementation. I have prepared a sample project where such implementation is demonstrated.
I hope this helps. If you have additional questions, feel free to contact me.
the Telerik team
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