protected bool   IsChineseLetter(string input,int index)
     ......{
        int code = 0;
        int chfrom = Convert.ToInt32("4e00", 16);    //范围（0x4e00～0x9fff）转换成int（chfrom～chend）
        int chend = Convert.ToInt32("9fff", 16);
        if (input != "")
         ......{
             code = Char.ConvertToUtf32(input, index);    //获得字符串input中指定索引index处字符unicode编码
           
           if (code >= chfrom && code <= chend)    
             ......{
                return true;     //当code在中文范围内返回true

             }
            else
             ......{
                 return false ;    //当code不在中文范围内返回false
             }
         }
          return false;
 }