At the moment, the selection behavior of the NumericTextBox can vary depending on the Format - the Format is what is shown when the input does not have focus, and the Decimals control the actual number the user will see when they focus. Of both differ (for example, the Format has more decimal places, or some other information like a unit of measurement), the input value changes on focus, which removes the selection (highglight).
I would like the numeric textbox to always select all its content when it gets focused (either with the Tab key, or with a click).
Note on general input behavior - using Tab to focus in a field usually defaults to all the contents being selected, while a click results in a cursor without selection.
The request is initially opened for the NumericTextBox but also targets some other components that incorporate inputs, such as DatePicker.