.net 泛型集合排序，查找

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Services;
using System.Web.Script.Serialization;
using System.Xml;
using System.Collections;
using System.Linq;

/// <summary>
///WSxml 的摘要说明
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
//若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。 
[System.Web.Script.Services.ScriptService]
public class WSxml : System.Web.Services.WebService {

    public WSxml () {

        //如果使用设计的组件，请取消注释以下行 
        //InitializeComponent(); 
    }

    [WebMethod]
    public string HelloWorld() {
        return "Hello World";
    }
    [WebMethod]
    public string saveXml(string cName, string age, string mobile, string email, string ads)
    {
        DateTime dt = DateTime.Now;
        string cdate = dt.ToString();
        XmlDocument xmldoc = new XmlDocument();
        string xmlFilePath = HttpContext.Current.Server.MapPath("~/data/content.xml");
        xmldoc.Load(xmlFilePath);

        //查找根节点
        XmlNode chat = xmldoc.SelectSingleNode("chat");
        //使用xpath表达式选择文档中所有的tp子节点
        XmlNodeList typeNodeList = xmldoc.SelectNodes("/chat/tp");
        string str = string.Empty;

        //定义一个List泛型集合
        List<string> mlist = new List<string>();

        if (typeNodeList != null)
        {
            string mbl = string.Empty;
            foreach (XmlNode tpNode in typeNodeList)
            {
                //通过Attributes获得属性名字为mobile的属性
                mbl = tpNode.Attributes["mobile"].Value;
                //循环将mobile加入List泛型集合里
                mlist.Add(mbl);
            }

        }
        //查找是否存在List
        if (mlist.Contains(mobile))
        {
            return "您的手机号码已被注册，请勿重复注册";
        }
        //创建节点
        XmlElement infor = xmldoc.CreateElement("tp");
        infor.SetAttribute("cName", cName);
        infor.SetAttribute("age", age);
        infor.SetAttribute("mobile", mobile);
        infor.SetAttribute("email", email);
        infor.SetAttribute("ads", ads);
        infor.SetAttribute("cdate", cdate);
        //存入根节点，保存文件
        chat.AppendChild(infor);
        xmldoc.Save(xmlFilePath);

        return "恭喜您注册成功!";
    }

    [WebMethod]
    public string readxmlTable()
    {
        XmlDocument xmldoc = new XmlDocument();
        string xmlFilePath = HttpContext.Current.Server.MapPath("~/data/content.xml");
        xmldoc.Load(xmlFilePath);

        //使用xpath表达式选择文档中所有的tp子节点
        XmlNodeList typeNodeList = xmldoc.SelectNodes("/chat/tp");
        string str = string.Empty;
        //定义一个SortedDictionary泛型集合
        SortedDictionary<string, string> sd = new SortedDictionary<string, string>();

        if (typeNodeList != null)
        {
            string cName = string.Empty, age = string.Empty, mobile = string.Empty, email = string.Empty, ads = string.Empty, cdate = string.Empty;
            
            foreach (XmlNode tpNode in typeNodeList)
            {
                //通过Attributes获得属性名字为cName的属性
                cName = tpNode.Attributes["cName"].Value;
                age = tpNode.Attributes["age"].Value;
                mobile = tpNode.Attributes["mobile"].Value;
                email = tpNode.Attributes["email"].Value;
                ads = tpNode.Attributes["ads"].Value;
                cdate = tpNode.Attributes["cdate"].Value;

                sd.Add(cdate, cName + "," + age + "," + mobile + "," + email + "," + ads );
            }
            //foreach (KeyValuePair<string, string> item in sd) 为正序asc

            //使用泛型集合和linq将时间类型倒序desc排列
            foreach (KeyValuePair<string, string> item in sd.Reverse())
            {
                str += item.Value + "," + Convert.ToDateTime(item.Key).ToString("yyyy年MM月dd日HH时mm分") + "|";
            }
        }
            return str.Substring(0, str.Length - 1);
    }
}