PrepareCommand

        /// <summary>
        /// 执行参数查询
        /// </summary>
        /// <param name="cmd">数据库执行命令</param>
        /// <param name="conn">数据库连接命令</param>
        /// <param name="trans">事务</param>
        /// <param name="cmdText">查询语句</param>
        /// <param name="cmdParms">查询参数</param>
        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, string cmdText, SqlParameter[] cmdParms)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            if (trans != null)
                cmd.Transaction = trans;    //指定SqlCommand类的事务
            cmd.CommandType = CommandType.Text;//指定sqlcommand类的CommandText属性的解释类型
            if (cmdParms != null)//如果插入的参数不为空，则foreach循环遍历加入到SqlCommand类的参数属性中
            {
                foreach (SqlParameter parameter in cmdParms)
                {
                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&
                        (parameter.Value == null))
                    {
                        parameter.Value = DBNull.Value;
                    }
                    cmd.Parameters.Add(parameter);
                }
            }