Introduction:

In today's digital world, it is crucial to validate user inputs and parsed data, especially when it comes to Internet Protocol version 4 (IPv4) addresses. These addresses are fundamental in identifying and communicating with devices on a network. In this blog, we will explore multiple methods in C# to validate whether a given string represents a valid IPv4 address. We will provide code examples, explanations, and the corresponding output for each method.

Method 1: Regular Expressions

Regular expressions offer a powerful tool for pattern matching, making them a suitable option for validating an IPv4 address. We can define a regular expression pattern that matches the required format of an IPv4 address, consisting of four numbers separated by periods, with each number ranging from 0 to 255.

using System;
using System.Text.RegularExpressions;

public class IPv4Validator
{
    public bool ValidateIPv4AddressRegex(string ipAddress)
    {
        string pattern = @"^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$";
        Regex regex = new Regex(pattern);
        return regex.IsMatch(ipAddress);
    }
}

Output:

Let's test the ValidateIPv4AddressRegex method with a few examples:

IPv4Validator validator = new IPv4Validator();
Console.WriteLine(validator.ValidateIPv4AddressRegex("192.168.0.1"));  // Output: True
Console.WriteLine(validator.ValidateIPv4AddressRegex("256.0.0.0"));     // Output: False
Console.WriteLine(validator.ValidateIPv4AddressRegex("192.168.0"));     // Output: False

Method 2: Splitting and Parsing

An alternative approach is to split the input string into its four components using the period as a delimiter. Then, we can check if each component is a valid integer within the range of 0 to 255. This method avoids the complexity of regular expressions and allows us to leverage the built-in integer parsing functions.

public class IPv4Validator
{
    public bool ValidateIPv4AddressSplit(string ipAddress)
    {
        string[] components = ipAddress.Split('.');
        if (components.Length != 4)
            return false;

        foreach (string component in components)
        {
            if (!int.TryParse(component, out int value) || value < 0 || value > 255)
                return false;
        }

        return true;
    }
}

Output:

Let's test the ValidateIPv4AddressSplit method with a few examples:

IPv4Validator validator = new IPv4Validator();
Console.WriteLine(validator.ValidateIPv4AddressSplit("192.168.0.1"));  // Output: True
Console.WriteLine(validator.ValidateIPv4AddressSplit("256.0.0.0"));     // Output: False
Console.WriteLine(validator.ValidateIPv4AddressSplit("192.168.0"));     // Output: False

Method 3: IPAddress Class

C# provides the IPAddress class, which offers built-in functionality for IP address validation. We can utilize the TryParse method of this class to validate an IPv4 address.

using System;
using System.Net;

public class IPv4Validator
{
    public bool ValidateIPv4AddressIPAddress(string ipAddress)
    {
        return IPAddress.TryParse(ipAddress, out IPAddress parsedIP) && parsedIP.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork;
    }
}

Output:

Let's test the ValidateIPv4AddressIPAddress method with a few examples:

IPv4Validator validator = new IPv4Validator();
Console.WriteLine(validator.ValidateIPv4AddressIPAddress("192.168.0.1"));  // Output: True
Console.WriteLine(validator.ValidateIPv4AddressIPAddress("256.0.0.0"));     // Output: False
Console.WriteLine(validator.ValidateIPv4AddressIPAddress("192.168.0"));     // Output: False

Conclusion:

In this blog, we explored three different methods to validate whether a given string represents a valid IPv4 address in C#. We started with regular expressions, providing a pattern that matches the format of an IPv4 address. We then explored an alternative method using string splitting and integer parsing. Finally, we showcased the IPAddress class, which offers built-in functionality for IP address validation.