c#调用oracle储存过程，返回字符串！

--储存过程如下 
create   or   replace   procedure   UpdateIBLocationId(Messages   out   varchar2,PIBName   in   varchar2) 
as   
    msg   varchar2(100); 
begin   
        select   ibcode   into   oldIBCode   from   p010b001.ib_recognize_declare   where   ibname=PIBName;         
        ...... 
Messages   := "成功！ "; 
end   UpdateIBLocationId; 
//C#调用如下， 
cmd   =   new   OracleCommand( "UpdateIBLocationId ",   con); 
                        cmd.CommandType   =   CommandType.StoredProcedure;                         p1   =   new   OracleParameter( "result ",   OracleType.VarChar,500); 
                        p1.Direction   =   System.Data.ParameterDirection.ReturnValue; 
                        cmd.Parameters.Add(p1);                         p2   =   new   OracleParameter( "PIBName ",   OracleType.VarChar,   20); 
                        p2.Direction   =   System.Data.ParameterDirection.Input; 
                        p2.Value   =   ibName[i];   cmd.Parameters.Add(p2); 
try 
                        { 
                                con.Open(); 
                                cmd.ExecuteNonQuery(); 
                                //DataSet   ds   =   new   DataSet();   
                              //IDbDataAdapter   da   =   new   System.Data.OracleClient.OracleDataAdapter(cmd); 
                                //da.Fill(ds);     
                              //   Message   +=ds.Tables[0]   +   " <br/> ------------------------------------------------------------ <br/> "; 
                        } 
                        finally 
                        { 
                                if   (con   !=   null) 
                                { 
                                        con.Close(); 
                                } 
                        } //调用报错 
“/”应用程序中的服务器错误。 
-------------------------------------------------------------------------------- ORA-06550:   第   1   行,   第   18   列:   
PLS-00306:   调用   'UPDATEIBLOCATIONID '   时参数个数或类型错误 
ORA-06550:   第   1   行,   第   7   列:   
PL/SQL:   Statement   ignored 请问如何得到返回参数Messages   的值