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

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.

add something like this to your code

  if( IPAddress.Parse(a).AddressFamily == AddressFamily.InterNetwork )
  // IPv4 address

Here's a function I use:

public static string GetIP4Address()
{
    string IP4Address = String.Empty;

    foreach (IPAddress IPA in Dns.GetHostAddresses(Dns.GetHostName()))
    {
        if (IPA.AddressFamily == AddressFamily.InterNetwork)
        {
            IP4Address = IPA.ToString();
            break;
        }
    }

    return IP4Address;
}

---

As an enumerable:

public static IEnumerable<string> GetIP4Addresses()
{
    return Dns.GetHostAddresses(Dns.GetHostName())
        .Where(IPA => IPA.AddressFamily == AddressFamily.InterNetwork)
        .Select(x => x.ToString());
}