Is there a way to run a Linq query within the after script of a customization?

I’m trying to execute a Linq statement within an After Field Change method
private void ShipDtl_AfterFieldChange(object sender, DataColumnChangeEventArgs args)

but I’m not getting past the test code as the Db is not defined. Anyone have any idea on what the declare needs to look like? Would I need to add a Linq using statement as well?

Or is there a better way to read an unrelated table from within the method?