arrow keys in datagrid

[william humphrey]

If I have a new stack with a list field and a datagrid both with rows of
data in them the arrow keys behave differently. In the list field you can
select a row and then, using the arrow keys, move to a row above or below.
In the datagrid you can select a row but the arrow keys will not move that
selection to a row above or below.

How do you get the arrow keys to have the same behaviour in a datagrid as
they do in a list field?

thnks