Thomas,
To be able to use a drop down filter, you need to have the columns be either an enumeration or an association. Attributes like City are a good candidate to be an associated entity (i.e. a lot of values, as a developer you don't really have access to a complete list of city names). Attributes like State are a good candidate to be an enumeration (i.e. small number of values, the list is static).
Hope that helps,
Mike
Hi Thomas,
If you want to use dropdown filter then you have to take the value like enumeration.
For string column you have to use text filter