How to convert CIDR subnet mask to hex format?

Tell FFFFFFFE how to get a value equal to FFFFFFFE turns out to output only EFFFF in reverse order and without the first two characters FF

Source Code: # 1

 var cidr = 23; var zeroBits = 32 - cidr; var result = uint.MaxValue; result &= (uint)((((ulong)0x1 << cidr) - 1) << zeroBits); result = (uint)IPAddress.HostToNetworkOrder((int)result); textBoxHex.Text = result.ToString("X");