C#读取xml文件

~/Config/Config.xml 文件： 

<?xml version="1.0" encoding="utf-8" ?>
<project> 
<function name="Account">
　　<attribute name="UserID" value="123456"></attribute>
</project>

公用类和方法：
using System;
using System.Xml;

namespace Common
{
    /// <summary>
    /// Summary description for XMLHelper.
    /// </summary>
    public class XMLHelper
    {
        public XMLHelper()
        {
            //
            // TODO: Add constructor logic here
            //
        }
        public static string ReadXML(string Function,string Attribute)
        {
            string returnValue = string.Empty;
            try
            {
                XmlDocument xmlDoc = new XmlDocument();
                xmlDoc.Load(System.Web.HttpContext.Current.Server.MapPath("~/Config/Config.xml"));
                XmlNode xn=xmlDoc.SelectSingleNode("project");
                XmlNodeList xnl=xn.ChildNodes;
                foreach(XmlNode xnf in xnl)
                {
                    if(xnf.Attributes.GetNamedItem("name").Value.Equals(Function))
                    {
                        XmlNodeList xnl2 = xnf.ChildNodes;
                        foreach(XmlNode xnf2 in xnl2)
                        {
                            XmlElement xe=(XmlElement)xnf2;
                            if(xe.GetAttribute("name").Equals(Attribute))
                            {
                                returnValue = xe.GetAttribute("value");
                                break;
                            }
                        }
                        break;
                    }
                }

                return returnValue;
            }
            catch(Exception ex)
            {
                return ex.Message;
            }
        }
    }
}

调用：
using Common;
string userid= XMLHelper.ReadXML("Account", "UserID"); //userid="123456".