Problem setting a computed-column

I am trying to set this col but I get an error:

FirstName + (CASE WHEN LEN(FirstName + LastName) > 0 THEN ' ' ELSE '') + LastName

From stackoverflow

• FirstName + (CASE WHEN LEN(FirstName + LastName) > 0 THEN ' ' ELSE '' end) + LastName
  

  missing the end

  Wahid Bitar : But what if last name length was 0 ?

  cmsjr : I was just addressing the OP's syntax problem, not his approach.

• You should close CASE with END and also, to my opinion, the following value will be better:

  FirstName + (CASE WHEN LEN(FirstName) > 0 AND LEN(LastName) > 0 THEN ' ' ELSE '' END) + LastName
  

  Shimmy : Good point about counting the chars and sum them vs. concatenating strings which cost more performance.