sql trigger & c#

Question

Hi.why my error message in sql trigger,doesn't show in c#?

while this code run correct in c#. 

 

CREATE TRIGGER [dbo].[trg_CheckBalance_me]

ON [dbo].[st_havaleh_info]

FOR INSERT,update

AS

BEGIN

SET NOCOUNT ON;

if ((select count_kala from st_seating where Code_kala=(select code_material from inserted )) < ((select count_unit from inserted)-(select count_unit from deleted)))

begin

ROLLBACK TRAN;

RAISERROR ('count of materials are low',16,1);

return

end

END;

go