internal static class XmlUtil
    {
        internal static XmlDocument doc;
        internal static string path;

        //在以下情況下執行該函數：1).當class不為static，實例化class時；2).當調用靜態字段、方法、屬性等時
        //但該函數僅執行一次
        static XmlUtil()
        {
            path = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
            path 
 
= Path.Combine(path, "Config.xml");
            doc = new XmlDocument();
            doc.Load(path);
        }
        
        internal static void SetValue(string valueName, string value)
        {
            XmlNode node = doc.DocumentElement.SelectSingleNode(valueName);
            node.InnerText 
 
= value;
            doc.Save(path);
        }

        internal static string GetValue(string valueName)
        {
            XmlNode node = doc.DocumentElement.SelectSingleNode(valueName);
            string result = node.InnerText;
            return result;
        }

    }

用法：

        static
 
 void Main(string[] args)
        {
            string v1 = XmlUtil.GetValue(@"/config/A2/AA1");
            Console.WriteLine(v1);

            v1 = XmlUtil.GetValue(@"A2/AA1");
            Console.WriteLine(v1);

            Console.ReadLine();
        }

C#讀取xml文件靜態類