Output parameter issue in sql server and c# -

why if have stored procedure created output parameter, i'm getting following error:

sp_dts_insertlsrbatch expects parameter @errormsg not supplied

stored procedure code:

set ansi_nulls on set quoted_identifier on go   alter procedure [dbo].[sp_dts_insertlsrbatch]       @lsrnbr varchar(10),     @batchnbr varchar(10),     @errormsg varchar(20) output begin        set nocount on;          if not exists(select *                 tbldts_lsrbatch (nolock)                  lsrnbr=@lsrnbr , batchnbr=@batchnbr)     begin            -- check if batchnbr exists under lsr         -- if not add (lsr, batchnbr) else error          if not exists(select *                 tbldts_lsrbatch (nolock)                  batchnbr=@batchnbr)                 insert tbldts_lsrbatch (lsrnbr,batchnbr) values (@lsrnbr, @batchnbr)                else                 set @errormsg = 'batch dif lsr'          end end 

c# code:

sqlconnection conn = new sqlconnection(connstr);  try {    conn.open();                     (int = 0; <= lbxbatch.items.count - 1; i++)    {        sqlcommand cmd = new sqlcommand("sp_dts_insertlsrbatch", conn);        cmd.parameters.add(new sqlparameter("@lsrnbr", txtlsr.text));        cmd.parameters.add(new sqlparameter("@batchnbr", lbxbatch.items[i].tostring()));        //output parameter "errormsg"        sqlparameter perrormsg = new sqlparameter("@errormsg", sqldbtype.varchar, 20);        perrormsg.direction = parameterdirection.output;         cmd.commandtype = commandtype.storedprocedure;        cmd.executenonquery();  <--- error 

in code haven't added perrormsg parameter. add line:

cmd.parameters.add(perrormsg);