C# 根据IP地址获取城市

using System;
using System.IO;
using System.Net;
using System.Text;
using System.Web.Script.Serialization;

namespace IpUtils
{
    public class IpDetail
    {
        public String Ret { get; set; }

        public String Start { get; set; }

        public String End { get; set; }

        public String Country { get; set; }

        public String Province { get; set; }

        public String City { get; set; }

        public String District { get; set; }

        public String Isp { get; set; }

        public String Type { get; set; }

        public String Desc { get; set; }
    }

    public class IpHelper
    {
        /// <summary>
        /// 获取IP地址的详细信息，调用的借口为
        /// http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=json&ip={ip}
        /// </summary>
        /// <param name="ipAddress">请求分析得IP地址</param>
        /// <param name="sourceEncoding">服务器返回的编码类型</param>
        /// <returns>IpUtils.IpDetail</returns>
        public static IpDetail Get(String ipAddress,Encoding sourceEncoding)
        {
            String ip = string.Empty;
            if(sourceEncoding==null)
                sourceEncoding = Encoding.UTF8;
            using (var receiveStream = WebRequest.Create("http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=json&ip="+ipAddress).GetResponse().GetResponseStream())
            {
                using (var sr = new StreamReader(receiveStream, sourceEncoding))
                {
                    var readbuffer = new char[256];
                    int n = sr.Read(readbuffer, 0, readbuffer.Length);
                    int realLen = 0;
                    while (n > 0)
                    {
                        realLen = n;
                        n = sr.Read(readbuffer, 0, readbuffer.Length);
                    }
                    ip = sourceEncoding.GetString(sourceEncoding.GetBytes(readbuffer, 0, realLen));
                }
            }
            return  !string.IsNullOrEmpty(ip)?new JavaScriptSerializer().Deserialize<IpDetail>(ip):null;
        }
    }

    public class EncodingHelper
    {
        public static String GetString(Encoding source, Encoding dest, String soureStr)
        {
            return dest.GetString(Encoding.Convert(source, dest, source.GetBytes(soureStr)));
        }

        public static String GetString(Encoding source, Encoding dest, Char[] soureCharArr, int offset, int len)
        {
            return dest.GetString(Encoding.Convert(source, dest, source.GetBytes(soureCharArr, offset, len)));
        }
    }
}

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