I'm not sure if you need perfomance for doing this, but here is the fastest method to convert byte[] to hex string that I can think of :
static readonly char[] hexchar = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
public static string HexStr(byte[] data, int offset, int len, bool space = false)
{
int i = 0, k = 2;
if (space) k++;
var c = new char[len * k];
while (i < len)
{
byte d = data[offset + i];
c[i * k] = hexchar[d / 0x10];
c[i * k + 1] = hexchar[d % 0x10];
if (space && i < len - 1) c[i * k + 2] = ' ';
i++;
}
return new string(c, 0, c.Length);
}