c# - How do I determine the local host’s IPv4 addresses?

Question

How do I get only Internet Protocol version 4 addresses from Dns.GetHostAddresses()? I have the code below, and it gives me IPv4 and IPv6 addresses. I have to make it work with boxes that have multiple IPv4 addresses.

IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());
private void get_IPs()
    {
        foreach (IPAddress a in localIPs)
        {
           server_ip = server_ip + a.ToString() + "/";
        }
    }

Answer 1

From my blog:

/// <summary> 
/// This utility function displays all the IP (v4, not v6) addresses of the local computer. 
/// </summary> 
public static void DisplayIPAddresses() 
{ 
    StringBuilder sb = new StringBuilder(); 

    // Get a list of all network interfaces (usually one per network card, dialup, and VPN connection) 
    NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces(); 

    foreach (NetworkInterface network in networkInterfaces) 
    { 
        // Read the IP configuration for each network 
        IPInterfaceProperties properties = network.GetIPProperties(); 

        // Each network interface may have multiple IP addresses 
        foreach (IPAddressInformation address in properties.UnicastAddresses) 
        { 
            // We're only interested in IPv4 addresses for now 
            if (address.Address.AddressFamily != AddressFamily.InterNetwork) 
                continue; 

            // Ignore loopback addresses (e.g., 127.0.0.1) 
            if (IPAddress.IsLoopback(address.Address)) 
                continue; 

            sb.AppendLine(address.Address.ToString() + " (" + network.Name + ")"); 
        } 
    } 

    MessageBox.Show(sb.ToString()); 
}

In particular, I do not recommend Dns.GetHostAddresses(Dns.GetHostName());, regardless of how popular that line is on various articles and blogs.