关于XML文档操作类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;

namespace ZW.ClassLibrary
{
   public class XmlHelpers
    {
       /// <summary>
       /// XML文档
       /// </summary>
       XmlDocument xd = new XmlDocument();

       /// <summary>
       /// 从文件中获取XmlDocument对象
       /// </summary>
       /// <param name="file">xml文档</param>
       /// <param name="type">文档类型</param>
       public XmlHelpers(string file, string type)
       {
           if (type == "path")
           {
               XmlTextReader xr = new XmlTextReader(file);
               xd.Load(xr);
               xr.Close();
           }

           if (type == "text")
           {
               xd.LoadXml(file);
           }
       }

       /// <summary>
       /// 获取第一个匹配节点的属性值
       /// </summary>
       /// <param name="nodePath"></param>
       /// <param name="attrName"></param>
       /// <returns></returns>
       public string GetAttribute(string nodePath, string attrName)
       {
           XmlNode xn = xd.SelectSingleNode(nodePath);
           if (xn == null) //检测节点是否存在
           {
               return "";
           }
           if (xn.Attributes[attrName] == null) //检测属性是否存在
           {
               return "";
           }

           return xn.Attributes[attrName].Value;
       }

       /// <summary>
       /// 获取某个节点
       /// </summary>
       /// <param name="nodePath"></param>
       /// <returns></returns>
       public XmlNode GetNode(string nodePath)
       {
           XmlNode xn = xd.SelectSingleNode(nodePath);
           return xn;
       }

       /// <summary>
       /// 获取某个节点子集合指定属性值的节点
       /// </summary>
       /// <param name="nodePath">父节点</param>
       /// <returns></returns>
       public XmlNode GetNode(string nodePath, string attrName, string attrValue)
       {
           XmlNodeList xl = GetChildNode(nodePath);
           if (xl != null)
           {
               foreach (XmlNode node in xl)
               {
                   if (node.Attributes[attrName] != null) //检测属性是否存在
                   {
                       if (node.Attributes[attrName].Value.Trim() == attrValue)
                       {
                           return node;
                       }
                   }
               }
           }
           return null;
       }

       /// <summary>
       /// 获取某个节点上的子节点
       /// </summary>
       /// <param name="nodePath"></param>
       /// <returns></returns>
       public XmlNodeList GetChildNode(string nodePath)
       {
           XmlNodeList xl = null;
           XmlNode xn = xd.SelectSingleNode(nodePath);
           if (xl != null)
           {
               xl = xd.ChildNodes;
           }
           return xl;
       }
    }
}