Subnetmask.cs

using System.Collections.Generic;
using System.Net;

namespace NETworkManager.Models.Network;

public static class Subnetmask
{
    public static List<SubnetmaskInfo> List => GenerateList();

    private static List<SubnetmaskInfo> GenerateList()
    {
        var list = new List<SubnetmaskInfo>();

        for (var i = 2; i < 31; i++)
            list.Add(GetFromCidr(i));

        return list;
    }

    public static SubnetmaskInfo GetFromCidr(int cidr)
    {
        return new SubnetmaskInfo
        {
            CIDR = cidr,
            Subnetmask = ConvertCidrToSubnetmask(cidr)
        };
    }

    public static string ConvertCidrToSubnetmask(int cidr)
    {
        var bits = new string('1', cidr);

        return IPv4Address.ToHumanString(bits.PadRight(32, '0'));
    }

    public static int ConvertSubnetmaskToCidr(IPAddress subnetmask)
    {
        return string.Join("", IPv4Address.ToBinaryString(subnetmask.ToString()).Replace(".", "").TrimEnd('0')).Length;
    }
}