Code
static   void   Main()   
  {   
        int   i   =   446;   
        string   hex   =   i.ToString(   "X"   /*   or   x   *   );   
        Console.WriteLine(   hex   );   
          
        int   j   =   HexToInt(   hex   );   
        Console.WriteLine(   j   );   
  }         
          
        static   int   HexToInt(string   hex)   
                  {   
                          hex   =   Regex.Replace(hex,   "^0x",   "",   RegexOptions.IgnoreCase);   
    
                          if   (Regex.IsMatch(hex,   "[g-z]",   RegexOptions.IgnoreCase))   
                          {   
                                  throw   new   Exception("Invalid   Hexadecimal   Expression.:   0x"   +   hex);   
                          }   
    
                          char[]   chars   =   hex.ToUpper().ToCharArray();   
                          Array.Reverse(chars);   
    
                          int   dec   =   0;   
                          for   (int   i   =   0;   i   <   chars.Length;   i++)   
                          {   
                                  dec   +=   HexMapping(chars[i])   *   (int)Math.Pow(16,   i);   
                          }   
    
                          return   dec;   
                  }   
    
                  static   int   HexMapping(char   c)   
                  {   
                          switch   (c)   
                          {   
                                  case   '0':   
                                          return   0;   
                                  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   :   
                                          throw   new   Exception("Invalid   Hexadecimal   Character   :"   +   c.ToString());   
                          }   
                  }