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(); 
 		} 
 	} 
 }