Introduction
Using help of NetworkInterface class of System.Net.NetworkInformation the internet connection can be detected. see the code below for more details
Code

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace MyCRND

{

class Program

{

static void Main(string[] args)

{

Console.WriteLine((System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable() == true ? "Connected" : "Not Connected"));

Console.ReadLine();

}

}

}