Dynamic "where" statement (Stored procedure)

Se attached code snippet. I need help to make the "whereStatement" correct.

If @guid is NOT blank I want the where statement to be like this:
where active='1'  and guid=@guid

If @guid is blank I want the where statement to be like this:
where active='1'  and codeID=@codeID

Thanks for all help :)

ALTER PROCEDURE [dbo].[spKodeDetaljPay] 
(
@codeid smallint,
@guid varchar(64)
)
AS
 
BEGIN
 
Select title, text, 
(Select name from tblPersonPay where tblCode.PersonID = tblPersonPay.PersonID) as Name,
(Select email from tblPersonPay where tblCode.PersonID = tblPersonPay.PersonID) as email from tblCode
where active='1' -- and " & whereStatement 
 
END

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