int d=10;
d.ToString("x") //或把x改为Ｘ，，，就变成了１６位的字符串了．
int x=Convert.ToInt32(d.ToString("x"),16);／／把１６进制的字符串变回１０进制的．

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());
}
}