Tsql Case

im 1 day new to sql server and trying to build a full name for a sp
so i am testing using :

DECLARE @SALvarchar(4)
DECLARE @Fnamevarchar(15)
DECLARE @MIvarchar(10)
DECLARE @Lnamevarchar(15)
DECLARE @Titlevarchar(25)
DECLARE @Contactvarchar(50)


SET @SAL = 'Mr.'
SET @Fname= 'Conrad'
SET @MI= null
SET @Lname= 'Bains'
SET @Title= null

SELECT @Contact +
CASE
WHEN @Sal IS NULL THEN '' + @Fname + ' '
WHEN @Mi IS NULL THEN + @Lname
ELSE +@Mi + ' ' + @Lname
WHEN @Title IS NULL THEN + ''
ELSE +', ' + @Title
END

the else is wrong not sure how to handle any help on my simpleton ?

THnks