Now you can use string code or a model enum (with Value attribute) in Query.Where for CodeIn and CodeEquals for all selection fields (Status, Priority, BillType, AssignedTo, Application, AssignedUsergroups, DisplayTypes, PerformedBy, PerformedFor, Impact, Probability, Lovs (combo, multicombo, toggle), Itempicker, Multiitempicker and PersonPicker. For personpickers emailaddress can be used. A model enum (with Value attribute) can also be used in .Equals and .In.

Note: Since Priority and Status are unique per ItemType, if you specify them in .Where make sure you use an interface with a ListContract if the itemtype is different from Action (Id: 5), if not it defaults to action.