Checking that a user has correctly entered an IP Address

Question

I am currently working on a C# project where I need to validate the text that a user has entered into a text box.

One of the validations required is that it checks to ensure that an IP address has been entered correctly.

How would I go about doing this validation of the IP address.

Thanks for any help you can provide.

Answer 1

You can use IPAddress.Parse Method .NET Framework 1.1. Or, if you are using .NET 4.0, see documentation for IPAddress.TryParse Method .NET Framework 4.

This method determines if the contents of a string represent a valid IP address. In .NET 1.1, the return value is the IP address. In .NET 4.0, the return value indicates success/failure, and the IP address is returned in the IPAddress passed as an out parameter in the method call.

edit: alright I'll play the game for bounty :) Here's a sample implementation as an extension method, requiring C# 3+ and .NET 4.0:

using System;
using System.Net;
using System.Text.RegularExpressions;

namespace IPValidator
{
    class Program
    {
        static void Main (string[] args)
        {
            Action<string> TestIP = (ip) => Console.Out.WriteLine (ip + " is valid? " + ip.IsValidIP ());

            TestIP ("99");
            TestIP ("99.99.99.99");
            TestIP ("255.255.255.256");
            TestIP ("abc");
            TestIP ("192.168.1.1");
        }

    }

    internal static class IpExtensions
    {
        public static bool IsValidIP (this string address)
        {
            if (!Regex.IsMatch (address, @"\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b"))
                return false;

            IPAddress dummy;
            return IPAddress.TryParse (address, out dummy);
        }
    }
}