How To Get Your IP Address in C#?

This guide explains how to retrieve both local and public IP addresses in C#. It covers using the DNS.GetHostEntry method for local IPs, querying an external API like api.ipquery.io for public IPs, and handling multiple network interfaces.

What is an IP Address?

An IP (Internet Protocol) address is a unique identifier for a device on a network. There are two main types of IP addresses.

1. Local (Private) IP Address: Used to identify devices within a local network (e.g., 192.168.x.x).
2. Public IP Address: Used to identify devices on the internet. This address is assigned by your ISP and is accessible outside your local network.

Getting the Local IP Address

To retrieve the local IP address, you can use the System.Net namespace in C#. This namespace provides classes and methods for working with network-related operations.

Example. Using DNS to Get the Host IP.

The simplest way to fetch the local IP address is through the DNS.GetHostEntry method.

using System;
using System.Linq;
using System.Net;

class Program
{
    static void Main()
    {
        string localIP = GetLocalIPAddress();
        Console.WriteLine($"Local IP Address: {localIP}");
    }

    static string GetLocalIPAddress()
    {
        var host = Dns.GetHostEntry(Dns.GetHostName());
        var ipAddress = host.AddressList
            .FirstOrDefault(ip => ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork);

        if (ipAddress == null)
            throw new Exception("No IPv4 address found for this machine.");

        return ipAddress.ToString();
    }
}

Key Details

• DNS.GetHostEntry retrieves the hostname and associated IP addresses.
• The AddressFamily filter ensures only IPv4 addresses are considered, excluding IPv6.

Getting the Public IP Address

A public IP address cannot be directly retrieved from the local system because it is managed by your router or ISP. To fetch your public IP, you'll typically query an external service.

Example. Fetching the Public IP from an API.

Here’s how you can use HttpClient to query a public IP lookup service.

using System;
using System.Net.Http;
using System.Threading.Tasks;
class Program
{
    static async Task Main()
    {
        string publicIP = await GetPublicIPAddressAsync();
        Console.WriteLine($"Public IP Address: {publicIP}");
    }
    static async Task<string> GetPublicIPAddressAsync()
    {
        using (var client = new HttpClient())
        {
            string url = "https://api.ipquery.io";
            var response = await client.GetStringAsync(url);
            return response.Trim();
        }
    }
}

Key Details

• API Used: https://api.ipquery.io returns the public IP in plain text.
• HttpClient: Handles the HTTP request and retrieves the response.
• Always ensure your application handles potential network exceptions.

Handling Multiple Network Interfaces

If your machine has multiple network interfaces (e.g., Ethernet, Wi-Fi), you might want to specify which interface to query. You can use the NetworkInterface class for more granular control.

Example. Enumerating All Network Interfaces.

using System;
using System.Net.NetworkInformation;
using System.Net.Sockets;
class Program
{
    static void Main()
    {
        foreach (var ip in GetAllLocalIPAddresses())
        {
            Console.WriteLine($"Found IP Address: {ip}");
        }
    }
    static string[] GetAllLocalIPAddresses()
    {
        var ipList = NetworkInterface.GetAllNetworkInterfaces()
            .Where(n => n.OperationalStatus == OperationalStatus.Up)
            .SelectMany(n => n.GetIPProperties().UnicastAddresses)
            .Where(a => a.Address.AddressFamily == AddressFamily.InterNetwork)
            .Select(a => a.Address.ToString())
            .ToArray();
        return ipList;
    }
}

Key Details

• Filters interface that are up and running.
• Retrieves all IPv4 addresses associated with those interfaces.

Common Pitfalls and Best Practices

1. Local vs. Public IP: Always clarify whether you need the local or public IP. Confusion between these can lead to incorrect implementations.
2. Error Handling: Network requests can fail due to various reasons (e.g., no internet). Always handle exceptions gracefully.
3. Privacy Considerations: Avoid logging or sharing sensitive IP details without user consent.
4. IPv6 Compatibility: Ensure your application accounts for IPv6 if needed.