如何自动识别判断url中的中文参数是GB2312还是Utf-8编码？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Text.RegularExpressions;

namespace ConsoleApplication2 {
class Program {
public static string DecodeURL2(String uriString) {
if (Regex.IsMatch(
HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("iso-8859-1")),
@"^(?:[x00-x7f]|[xe0-xef][x80-xbf]{2})+$" // 如果不考虑哪些什么拉丁文啊，希腊文啊。。。乱七八糟的外文，用这个短的正则
)) {
return HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("UTF-8"));
} else {
return HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("GB2312"));
}
}

public static string DecodeURL(String uriString) {
if (Regex.IsMatch(
HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("iso-8859-1")),
@"^(?:[x00-x7f]|[xfc-xff][x80-xbf]{5}|[xf8-xfb][x80-xbf]{4}|[xf0-xf7][x80-xbf]{3}|[xe0-xef][x80-xbf]{2}|[xc0-xdf][x80-xbf])+$"
)) {
return HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("UTF-8"));
} else {
return HttpUtility.UrlDecode(uriString, Encoding.GetEncoding("GB2312"));
}
}

public static void Main(string[] args) {
Console.WriteLine("----------------------------------------------");
Console.WriteLine(DecodeURL(".net%bc%bc%ca%f5"));
Console.WriteLine(DecodeURL(".net%e6%8a%80%e6%9c%af"));

Console.WriteLine("----------------------------------------------");
Console.WriteLine(DecodeURL("%B8%A7%CB%B3%C7%E0%CB%C9%D2%A9%D2%B5"));
Console.WriteLine(DecodeURL("%E6%8A%9A%E9%A1%BA%E9%9D%92%E6%9D%BE%E8%8D%AF%E4%B8%9A"));

Console.WriteLine("------------------↓↓↓下面的出问题↓↓↓------------------");

Console.WriteLine(DecodeURL("%E8%81%94%E9%80%9A")); // 正常
Console.WriteLine(DecodeURL("%C1%AA%CD%A8")); // 发生编码误认
// 编码误认，并没有好的解决方案，因为utf-8和gbk编码结果存在交叉， 我们都知道，记事本也都会出现这种情况

Console.WriteLine("------------------↑↑↑上面的出问题↑↑↑------------------");

Console.WriteLine(DecodeURL2("%E8%81%94%E9%80%9A")); // 正常
Console.WriteLine(DecodeURL2("%C1%AA%CD%A8")); // 不会误认
Console.WriteLine("----------------------------------------------");

Console.ReadKey();
}
}
}