Expression after case-statement

The syntax for a case when statement in SQL is as follows

Simple Caseexpression: Caseinput_expression whenWhen_expression ThenResult_expression[. .. n]      [ELSE else_result_expression] ENDsearched Caseexpression: Case      whenBoolean_expression ThenResult_expression[. .. n]      [ELSE else_result_expression] END

Where result_expression is supposed to be an arbitrary and valid expression, the same goes for MSDN. Can use this statement today, want to write a simple SELECT statement behind when, actually error.

Tried for a long time, and later wanted to try without a brace, and then succeeded.

 Caseod. ObjectType when 1  Then(SELECT TOP 1Structurename fromTbl_stationstructureWHEREStructuretype=2)     when 2  Then(SELECT TOP 1Structurename fromTbl_stationstructureWHEREStructureid=od. OBJECTID)END    

Expression after case-statement