Zachary.XiaoZhen - 夢想的天空

Linq to xml 這個東西出來好多年了,但一直沒有機會在項目中用到,前段時間,終于項目中一些地方需要用到xml作為數據源,于是就體驗了一把這個,感覺還挺不錯的,今天在此小結一下.

       首先我們來模擬一下一個真實的業務場景:在這里我們需要展示一個火車站上各個站臺上面燈光開關狀態.假設每個站臺一共6個開關,站臺我們用Station節點表示,站臺開關我們用SwitchNo來表示,在初始化(即默認狀態)的時候,我們需要表示成第一個站臺2個開關開著,第二個站臺3個開關開著,第三個站臺4個開關開著….

    那么我們可能需要的一個xml文件格式可能就是如下這個樣子: 

<?xml version="1.0" encoding="utf-8"?>
<Stations>
  <Station Id="1">
    <SwitchNo Id="1">1</SwitchNo>
    <SwitchNo Id="2">1</SwitchNo>
    <SwitchNo Id="3">0</SwitchNo>
    <SwitchNo Id="4">0</SwitchNo>
    <SwitchNo Id="5">0</SwitchNo>
    <SwitchNo Id="6">0</SwitchNo>
  </Station>
  <Station Id="2">
    <SwitchNo Id="1">1</SwitchNo>
    <SwitchNo Id="2">1</SwitchNo>
    <SwitchNo Id="3">1</SwitchNo>
    <SwitchNo Id="4">0</SwitchNo>
    <SwitchNo Id="5">0</SwitchNo>
    <SwitchNo Id="6">0</SwitchNo>
  </Station>
  <Station Id="3">
    <SwitchNo Id="1">1</SwitchNo>
    <SwitchNo Id="2">1</SwitchNo>
    <SwitchNo Id="3">1</SwitchNo>
    <SwitchNo Id="4">0</SwitchNo>
    <SwitchNo Id="5">0</SwitchNo>
    <SwitchNo Id="6">0</SwitchNo>
  </Station>
  <Station Id="4">
    <SwitchNo Id="1">0</SwitchNo>
    <SwitchNo Id="2">0</SwitchNo>
    <SwitchNo Id="3">1</SwitchNo>
    <SwitchNo Id="4">1</SwitchNo>
    <SwitchNo Id="5">0</SwitchNo>
    <SwitchNo Id="6">0</SwitchNo>
  </Station>
  <Station Id="5">
    <SwitchNo Id="1">1</SwitchNo>
    <SwitchNo Id="2">1</SwitchNo>
    <SwitchNo Id="3">1</SwitchNo>
    <SwitchNo Id="4">1</SwitchNo>
    <SwitchNo Id="5">1</SwitchNo>
    <SwitchNo Id="6">0</SwitchNo>
  </Station>
  <Station Id="6">
    <SwitchNo Id="1">1</SwitchNo>
    <SwitchNo Id="2">1</SwitchNo>
    <SwitchNo Id="3">1</SwitchNo>
    <SwitchNo Id="4">1</SwitchNo>
    <SwitchNo Id="5">1</SwitchNo>
    <SwitchNo Id="6">1</SwitchNo>
  </Station>
</Stations>

下面我們就從xml數據的創建/查詢/修改這三個方面簡單談一下吧.關于概念啥的就不啰嗦了,直接上代買吧.

1. 創建這個文件

/// <summary>
        /// 創建xml文件
        /// </summary>
        private void writeStationXmlData()
        {            
            string fileName = Path.Combine(dataPath, "StationWitch.xml");

            if (!Directory.Exists(dataPath))
                Directory.CreateDirectory(dataPath);

            if (File.Exists(fileName))
                return;

            var stationEleList = new List<XElement>();  //臨時緩存每個站臺節點

            //一共6個站臺,循環創建           
            for (int i = 1; i < 7; i++)
            {
                var xAttr = new XAttribute("Id", i);

                //臨時緩存每個每個站臺下的開關狀態
                var childList = new List<XElement>();       
                for (int j = 1; j < 7; j++)
                {
                    childList.Add(new XElement("SwitchNo", new XAttribute("Id", j), i >= j ? 1 : 0));
                }

                //構建一個站臺節點
                var stationEle = new XElement("Station", xAttr, childList.ToArray());
                stationEleList.Add(stationEle);
            }

            //構建Stations節點
            XElement xBody = new XElement("Stations", stationEleList.ToArray());

            //構建整個文檔
            XDocument doc = new XDocument(
                    new XDeclaration("1.0", "utf-8", "yes"), xBody);
            doc.Save(fileName);
        }

2. 讀取當前xml 文件并轉化為友好的類型

/// <summary>
        /// 查詢讀取每個站臺的開關狀態并轉化為keyValue鍵值對
        /// </summary>
        /// <returns></returns>
        public IList<KeyValue<int, int>> GetStationLightData()
        {
            writeStationXmlData();
            if (stationLightData == null)
            {
                stationLightData = new List<KeyValue<int, int>>();
                stationSwitchStatus = new List<KeyValue<int, bool>>();                

                //加載xml
                string fileName = Path.Combine(dataPath, "StationWitch.xml");
                XElement doc = XElement.Load(fileName);

                //讀取站臺列表
                var station = from s in doc.Descendants("Station")
                              select s;
                //遍歷站臺
                foreach (var st in station)
                {
                    //獲取每個站臺的開關集合 即SwitchNo節點
                    var st_switchs = st.Elements("SwitchNo");
                    var stationId = int.Parse(st.Attribute("Id").Value);
                    int light = 0;
                    foreach (var sw in st_switchs)
                    {
                        var swithNo = int.Parse(sw.Attribute("Id").Value);
                        bool isOn = sw.Value == "1";
                        if (isOn)
                            light += 20;
                        stationSwitchStatus.Add(new KeyValue<int, bool>(stationId, isOn, swithNo));
                    }
                    stationLightData.Add(new KeyValue<int, int>(stationId, light));
                }
            }
            return stationLightData;
        }

3.更新節點值(先查詢找到指定的節點 在更新后保存)

 /// <summary>
        /// 更新制定站臺中的指定開關的狀態,即更新制定Station->SwitchNo節點下值
        /// </summary>
        /// <param name="station"></param>
        /// <param name="switchNo"></param>
        /// <param name="isOn"></param>
        public void UpdateStationSwitchStatus(int station, int switchNo, bool isOn)
        {
            string fileName = Path.Combine(dataPath, "StationWitch.xml");
            //讀取數據
            XElement doc = XElement.Load(fileName);
            var up_station = doc.Descendants("Station")
                .Where(o => o.Attribute("Id").Value == station.ToString()).FirstOrDefault();

            //找出指定的節點
            var upSwitch = up_station.Elements("SwitchNo").FirstOrDefault(o => o.Attribute("Id").Value == switchNo.ToString());

            //更新
            if (upSwitch != null)
            {
                upSwitch.Value = isOn ? "1" : "0";
            }

            //保存為文件
            lock (sync)
            {
                doc.Save(fileName);
            }
        }

至此,xml的常規操作就介紹完了,希望能對有需要的同學有所幫助.