UTF-8编码的转换

UTF-8编码的转换（2）

在中文网站的开发中，无论你是否注意到，事实上系统都在使用某一种编码方式来处理中文，如GB2312,UTF-8等，前者是经常使用的代码页，而后者则能够兼容所有的客户访问端，是发展的方向。

在处理过程中常常能够见到的情形是在URL或者POST的数据中，中文被编码成为%E8%87%AA这样的形式，事实上，在.net中要将这些编码还原为UTF-8中文字符并不困难，原理与代码如下：
1.每个中文字符占3个字节并以%开始,因此%E8%87%AA是一个中文字符(自),而事实上E8,87,AA都是16进制的数字,分别为高4位和低4位
2.只要能够将每两个十六进制表示转换成为数字,并存入到byte中,然后将得到的Byte数组用UTF8解码器解码即可

  public class UTF8Operator
  {
   /// <summary>
   /// This method is used to convert the string from "%E6%9D%B1" to UTF8 Chinese Chracter
   /// </summary>
   /// <param name="theInput"></param>
   /// <returns></returns>
   public static string ConvertGB2UTF8(string theInput)
   {
    //Only the string whhich starts with % will be handled
    if (theInput.StartsWith("%"))
    {
     UTF8Encoding utf8 = new UTF8Encoding();

          String theString = theInput;
  
          Byte[] bytes = new byte[theString.Length*3/9];
         
          string [] split = theString.Split(Convert.ToChar("%"));
          int i=0;
          foreach (string s in split)
           {
           string inputStr = s.Trim();
           int theValue = 0;
           if(inputStr.Length == 2)
           {
            //Get the high position
            theValue = theValue + ConvertHexToDec(inputStr.Substring(0,1))*16;
            
            //Get the low position
            theValue = theValue + ConvertHexToDec(inputStr.Substring(1,1));
            //Only the index of bytes array is less than the length
            if (i < bytes.Length)
            {
             bytes = (byte)theValue;             
            }
            i++;         
           }
           }
                   
          //Use the UTF8Encoding object to convert the bytes to string
     string theResult = utf8.GetString(bytes);
     return theResult;     
    }
    else
    {
     return theInput;
    }
   }
   
   //Convert the Hex Code to Dec. A-15, E-14....
   public static int ConvertHexToDec(string theValue)
   {
    string myValue = theValue.Trim().ToUpper();
    
        switch(myValue)      
         {        
           case "1":  
               return 1;
           case "2":  
               return 2;
           case "3":  
               return 3;
           case "4":  
               return 4;
           case "5":  
               return 5;
           case "6":  
               return 6;
           case "7":  
               return 7;
           case "8":  
               return 8;
           case "9":  
               return 9;
           case "A":  
               return 10;
           case "B":  
               return 11;
           case "C":  
               return 12;
           case "D":  
               return 13;
           case "E":  
               return 14;
           case "F":  
               return 15;
           default:           
               return 0;
          }  
   }
  }