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)));
}
}
}