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1. RadDropDownList uses RadListControl to represents its items (RadListElement in fact). So if you change the theme of RadListControl in VisualStyleBuilder, this will change both the items in RadListControl and the items in the drop down of RadDropDownList.
2. To align the text of DateTimePicker, you need to set TextAlign property of RadTimeMaskedEditBoxElement. Currently, this property is not a RadProperty and can't be set through VisualStyleBuilder. However the desired behavior can be achieved easily through the code. For example:
.radDateTimePicker1.DateTimePickerElement.TextBoxElement.TextAlign = HorizontalAlignment.Right;
I hope this helps. If you have further questions, feel free to write back.
the Telerik team