how about a Property for the DateTimePicker that can switch on(true) / off (false) for writing in null values. In my case, I don't/can't set the InputField to disable but the user should not be allowed to set the date to null. It would be awesome if the Picker sets its own value automatically to the last valid value by loosing the focus. if there is in the beginning no value in the field its automatically set to the date of today.
I mean something like the winforms feature:
datePicker.NullDate = ...