ORA-06550 PLS-00306的问题 请大虾们帮忙看看！

Question

错误提示：
<?xml version="1.0" encoding="UTF-8"?>
<string xmlns="http://tempuri.org/">ORA-06550: 第 1 行, 第 7 列: PLS-00306: 调用 'PRO_ADD_USER' 时参数个数或类型错误 ORA-06550: 第 1 行, 第 7 列: PL/SQL: Statement ignored </string>
----- Create table
create table TEST_A
(
  USER_NO   NUMBER not null,
  USER_NAME VARCHAR2(20)
)
alter table TEST_A
  add constraint TEST_A_PK primary key (USER_NO)
  using index 
  tablespace USERS
----Create procedure
create or replace procedure pro_add_user(as_userno test_a.user_no%Type,
                                         as_username  test_a.user_name%Type,
                                         ret_text out varchar) as
begin  insert into test_a (user_no, user_name) values (as_userno, as_username);
  commit;
exception
  when NO_DATA_FOUND then
    ret_text := SUBSTR(SQLERRM, 1, 200);
    rollback;
  when others then
    ret_text := SUBSTR(SQLERRM, 1, 200);
    rollback;
end pro_add_user;----   [WebMethod]
        public string add_users(int user_no,string user_name)
        {
            string ls_message;
            OracleConnection con = new OracleConnection(ls_continct);
            ls_message = string.Empty;
            try
            {
                con.Open();
                try
                {
                    OracleCommand com = new OracleCommand("pro_add_user",con);
                    com.Parameters.Clear();
                    com.CommandType = CommandType.StoredProcedure;                    OracleParameter as_userno = new OracleParameter("as_userno", OracleType.Int16);
                    OracleParameter as_username = new OracleParameter("as_username", OracleType.VarChar,20);
                    OracleParameter as_texts = new OracleParameter("as_texts", OracleType.VarChar, 200);
                    
                    as_userno.Value = user_no;
                    as_username.Value = user_name;                    
                    as_userno.Direction = ParameterDirection.Input;
                    as_username.Direction = ParameterDirection.Input;
                    as_texts.Direction = ParameterDirection.Output;
                    com.Parameters.Add(as_userno);
                    com.Parameters.Add(as_username);                    
                    com.Parameters.Add(as_texts);
                    com.ExecuteNonQuery();
                    ls_message = com.Parameters["as_texts"].Value.ToString();
                }
                catch(OracleException oraerr)
                {
                    ls_message = oraerr.Message.ToString();
                }
                finally
                {
                   con.Close();
                }
            }
            catch (OleDbException err)
            {
                ls_message = err.ToString();
            }
            return ls_message;
       }---调试存储过程，信息可插入数据库

Answer 1

今天调试发现如果去掉存储过程的 ret_text out varchar，运行正常，就不提示出错。考虑到是不是因为ret_text为NULL，在执行存储过程过程中加入为ret_text赋值的语句，还是不行！！

Answer 2

在：
insert into test_a (user_no, user_name) values (as_userno, as_username);
   commit;后加入赋值：
   as_text='插入成功';执行成功，之后注释掉 as_text='插入成功'; 再次运行，执行成功！虽然暂时解决了，具体原因仍不明！

Answer 3

as_userno 参数中可能存在NULL值导致的吧