You need to have a reference to %system32%/FirewallAPI.dll

FwRuleModificationOnStartup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using NetFwTypeLib;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            AddOrUpdateRule();
            Console.ReadLine();
        }

        public static void AddOrUpdateRule()
        {
            const string ruleName = "TESTING_RESTRICTED_ACCESS";

            INetFwPolicy2 firewallPolicy = (INetFwPolicy2)Activator.CreateInstance(
                Type.GetTypeFromProgID("HNetCfg.FwPolicy2"));

            INetFwRule rule = null;

            try
            {
                rule = firewallPolicy.Rules.Item(ruleName);
                if (rule != null)
                {
                    ConfigureRule(rule, ruleName);
                    return;
                }

            }
            catch(Exception ex)
            {
            }            

            rule = (INetFwRule)Activator.CreateInstance(Type.GetTypeFromProgID("HNetCfg.FWRule"));
            ConfigureRule(rule, ruleName);
            firewallPolicy.Rules.Add(rule);
        }

        private static void ConfigureRule(INetFwRule rule, string ruleName)
        {
            const string programPath = @"E:\dev\CRun\ConsoleApp1\bin\Debug\ConsoleApp1.exe";

            rule.Action = NET_FW_ACTION_.NET_FW_ACTION_ALLOW;
            rule.Description = $"Allow Only specific IPs. Last updated on: {DateTime.Now}";
            rule.Direction = NET_FW_RULE_DIRECTION_.NET_FW_RULE_DIR_IN;
            rule.Enabled = true;
            rule.Protocol = (int)NET_FW_IP_PROTOCOL_.NET_FW_IP_PROTOCOL_TCP;

            rule.RemotePorts = "443";
            rule.RemoteAddresses = "10.30.50.60/32,45.67.89.45/32";
            rule.InterfaceTypes = "All";
            rule.Name = ruleName;
            rule.ApplicationName = programPath;
        }
    }
}