Sql Server WHERE IN with CASE

Question

How can we specify range of values from CASE inside WHERE clause?
This query of mine fails

declare @ProductType int

select * from Products 
where ProductLine in 
(
    case @ProductType
        when 1 then ('TVs')
        when 2 then ('Handsets', 'Mobiles') --fails here
        else ('Books')
    end
)

This wouldn't work either:

declare @ProductType int

select * from Products 
where (case @ProductType 
             when 1 then (ProductLine = 'TVs')
             when 2 then (ProductLine in  ('Handsets', 'Mobiles'))
             else (ProductLine = 'Books')
       end)

Answer 1

You cannot do that - you need to split it to several checks:

WHERE (ProductLine = 'TVs' AND @ProductType = 1)
   OR (ProductLine IN ('Handsets', 'Mobiles') AND @ProductType = 2)
   OR (ProductLine = 'Books' AND @ProductType NOT IN (1, 2))