关于sqlhelper 调用存储过程 获取 返回值和参数的问题

从微软petshop中提取的sqlhelper。 执行存储过程的时候，数据参数总是为null.

起初我以为自己的存储过程写错了，测试后发现没有问题。

又在网上找了一些文章，说SqlDataReader 关闭后可以访问等。还是没解决问题

后来仔细看了下sqlhelper的代码发现问题所在，如下，原来在执行ExecuteReader 后，cmd.Parameters.Clear();
清理了参数，当然获取不到了.终于可以睡觉啦

        /// <summary>
        /// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  SqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>A SqlDataReader containing the results</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);

            // we use a try/catch here because if the method throws an exception we want to 
            // close the connection throw code, because no datareader will exist, hence the 
            // commandBehaviour.CloseConnection will not work
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                //cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }