How do I get the network interface and its right IPv4 address?

foreach(NetworkInterface ni in NetworkInterface.GetAllNetworkInterfaces())
{
   if(ni.NetworkInterfaceType == NetworkInterfaceType.Wireless80211 || ni.NetworkInterfaceType == NetworkInterfaceType.Ethernet)
   {
       Console.WriteLine(ni.Name);
       foreach (UnicastIPAddressInformation ip in ni.GetIPProperties().UnicastAddresses)
       {
           if (ip.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
           {
               Console.WriteLine(ip.Address.ToString());
           }
       }
   }  
}

This should get you what you want. ip.Address is an IPAddress, that you want.

One line with Lamda:

using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Net.NetworkInformation;

var ipV4s = NetworkInterface.GetAllNetworkInterfaces()
    .Select(i => i.GetIPProperties().UnicastAddresses)
    .SelectMany(u => u)
    .Where(u => u.Address.AddressFamily == AddressFamily.InterNetwork)
    .Select(i => i.Address);

With some improvement, this code adds any interface to a combination:

private void LanSetting_Load(object sender, EventArgs e)
{
    foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
    {
        if ((nic.NetworkInterfaceType == NetworkInterfaceType.Ethernet) || (nic.NetworkInterfaceType == NetworkInterfaceType.Wireless80211)) //&& (nic.OperationalStatus == OperationalStatus.Up))
        {
            comboBoxLanInternet.Items.Add(nic.Description);
        }
    }
}

And when selecting one of them, this code returns the IP address of the interface:

private void comboBoxLanInternet_SelectedIndexChanged(object sender, EventArgs e)
{
    foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
    {
        foreach (UnicastIPAddressInformation ip in nic.GetIPProperties().UnicastAddresses)
        {
            if (nic.Description == comboBoxLanInternet.SelectedItem.ToString())
            {
                if (ip.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
                {
                    MessageBox.Show(ip.Address.ToString());
                }
            }
        }
    }
}