SUM WHERE

Experts,

I am trying to bring query which match following condition (where count(distinct SDDoc) = 1 and count(distinct case when Netvalue = '0' then 1 else null end) = 1) is it correct?

my code is

SELECT

      [Soldtopt],

	  [tradingname],
	  [DlvDate],
	  SUM(try_cast(Netvalue as float)) as Netvalue,
	 count(distinct SDDoc)  as Salesdoc ,
	 count(distinct case when Netvalue = '0' then 1 else null end) as ZeroValue ,

	count(distinct SDDoc) - count(distinct case when  Netvalue = '0' then 1 else null end) As Result



  FROM [FOC].[dbo].[foc]


 where count(distinct SDDoc) = 1 and count(distinct case when Netvalue = '0' then 1 else null end) = 1

	GROUP by Soldtopt,tradingname,DlvDate  ORDER BY  count (distinct SDDoc) DESC; 

received following error ,

Msg 147, Level 15, State 1, Line 20
An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.