QuizSystem/Quizzer-8/Quizzer/Extensions/IPAddressExtensions.cs

// Original: https://learn.microsoft.com/en-us/archive/blogs/knom/ip-address-calculations-with-c-subnetmasks-networks
using Microsoft.AspNetCore.HttpOverrides;
using System.Net;

namespace Quizzer.Extensions
{
    public static class IPAddressExtensions
    {
        public static IPAddress GetBroadcastAddress(this IPAddress address, IPAddress subnetMask)
        {
            byte[] ipAdressBytes = address.GetAddressBytes();
            byte[] subnetMaskBytes = subnetMask.GetAddressBytes();

            if (ipAdressBytes.Length != subnetMaskBytes.Length)
                throw new ArgumentException("Lengths of IP address and subnet mask do not match.");

            byte[] broadcastAddress = new byte[ipAdressBytes.Length];
            for (int i = 0; i < broadcastAddress.Length; i++)
            {
                broadcastAddress[i] = (byte)(ipAdressBytes[i] | (subnetMaskBytes[i] ^ 255));
            }
            return new IPAddress(broadcastAddress);
        }

        public static IPAddress GetNetworkAddress(this IPAddress address, IPAddress subnetMask)
        {
            byte[] ipAdressBytes = address.GetAddressBytes();
            byte[] subnetMaskBytes = subnetMask.GetAddressBytes();

            if (ipAdressBytes.Length != subnetMaskBytes.Length)
                throw new ArgumentException("Lengths of IP address and subnet mask do not match.");

            byte[] broadcastAddress = new byte[ipAdressBytes.Length];
            for (int i = 0; i < broadcastAddress.Length; i++)
            {
                broadcastAddress[i] = (byte)(ipAdressBytes[i] & (subnetMaskBytes[i]));
            }
            return new IPAddress(broadcastAddress);
        }

        /// <summary>
        /// Are addressA on the same network as addressB ?
        /// </summary>
        /// <param name="addressA"></param>
        /// <param name="addressB"></param>
        /// <param name="subnetMask"></param>
        /// <returns>True if A and B are on the same network.</returns>
        public static bool IsInSameSubnet(this IPAddress addressA, IPAddress addressB, IPAddress subnetMask)
        {
            IPAddress networkA = addressA.GetNetworkAddress(subnetMask);
            IPAddress networkB = addressB.GetNetworkAddress(subnetMask);

            return networkA.Equals(networkB);
        }
    }
}