MySql.Data.MySqlClient.MySqlConnection.Dispose C# (CSharp) Method

        protected override void Dispose(bool disposing)
        {
            if (State == ConnectionState.Open)
                Close();
            base.Dispose(disposing);
        }

        /// <summary> 
        /// 修改数据 
        /// </summary> 
        /// <param name="entity"></param> 
        /// <returns></returns> 
        public int Update(Policy entity)
        {
            string sql = "UPDATE  tb_policy SET agentType=@agentType,subject=@subject,content=@content,sender=@sender,attachment=@attachment,attachmentName=@attachmentName,creatTime=@creatTime,";
            sql = sql + " type=@type,validateStartTime=@validateStartTime,validateEndTime=@validateEndTime,isValidate=@isValidate,isDelete=@isDelete,deleteTime=@deleteTime,toAll=@toAll where sequence=@sequence ";

            //string sql = "UPDATE cimuser SET userNickName=@userNickName WHERE userid=@userid";
            using (MySqlConnection mycn = new MySqlConnection(mysqlConnection))
            {
                mycn.Open();
                MySqlCommand command = new MySqlCommand(sql, mycn);
                command.Parameters.AddWithValue("@agentType", entity.agentType);
                command.Parameters.AddWithValue("@sequence", entity.sequence);
                command.Parameters.AddWithValue("@subject", entity.subject);
                command.Parameters.AddWithValue("@content", entity.content);
                command.Parameters.AddWithValue("@sender", entity.sender);
                command.Parameters.AddWithValue("@attachment", entity.attachment);
                command.Parameters.AddWithValue("@attachmentName", entity.attachmentName);
                command.Parameters.AddWithValue("@creatTime", entity.creatTime);
                command.Parameters.AddWithValue("@type", entity.type);
                command.Parameters.AddWithValue("@validateStartTime", entity.validateStartTime);
                 command.Parameters.AddWithValue("@validateEndTime", entity.validateEndTime);
                command.Parameters.AddWithValue("@isValidate", entity.isValidate);
                command.Parameters.AddWithValue("@isDelete", entity.isDelete);
                command.Parameters.AddWithValue("@deleteTime", entity.deleteTime);
                command.Parameters.AddWithValue("@toAll", entity.toAll);
                int i = command.ExecuteNonQuery();
                mycn.Close();
                mycn.Dispose();
                return i;
            }
        }