CODEWITHSUNDEEP
c#validation
Boardy
Boardy

Reputation: 36205

Checking that a user has correctly entered an IP Address

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.

Upvotes: 6

Views: 11317

Answers (6)

user20493
user20493

Reputation: 5804

Here's my solution:

using System.Net.NetworkInformation;
using System.Net;

    /// <summary>
    /// Return true if the IP address is valid.
    /// </summary>
    /// <param name="address"></param>
    /// <returns></returns>
    public bool TestIpAddress (string address)
    {
        PingReply reply;
        Ping pingSender = new Ping ();

        try
        {
            reply = pingSender.Send (address);
        }
        catch (Exception)
        {
            return false;
        }

        return reply.Status == IPStatus.Success;
    }

Upvotes: 0

Ludovic Kuty
Ludovic Kuty

Reputation: 4954

I'd use a regex.

^((25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)\.){3}(25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)$

Using named groups, it could be clearer. It is written in Ruby. I don't know C# but I guess that the regex support is complete in that language and that named groups might exist.

 /(?<number>(25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){0}^(\g<number>\.){3}\g<number>$/

Upvotes: 1

Parmenion
Parmenion

Reputation: 299

It seems that you are only concerned with validating IPv4 IP Address strings in X.X.X.X format. If so, this code is straight forward for that task:

string ip = "127.0.0.1";
string[] parts = ip.Split('.');
if (parts.Length < 4)
{
    // not a IPv4 string in X.X.X.X format
}
else
{
    foreach(string part in parts)
    {
        byte checkPart = 0;
        if (!byte.TryParse(part, out checkPart))
        {
            // not a valid IPv4 string in X.X.X.X format
        }
    }
    // it is a valid IPv4 string in X.X.X.X format
}

Upvotes: 5

Jon Hanna
Jon Hanna

Reputation: 113272

insta's answer was closer before he added the incorrect regexp.

public static bool IsValidIP(string ipAddress)
{
  IPAddress unused;
  return IPAddress.TryParse(ipAddress, out unused);
}

Or since the OP doesn't want to include integer IPv4 addresses that aren't full dotted quads:

public static bool IsValidIP(string ipAddress)
{
  IPAddress unused;
  return IPAddress.TryParse(ipAddress, out unused)
    &&
    (
        unused.AddressFamily != AddressFamily.InterNetwork
        ||
        ipAddress.Count(c => c == '.') == 3
    );
}

Testing:

IsValidIP("fe80::202:b3ff:fe1e:8329") returns true (correct).

IsValidIP("127.0.0.1") returns true (correct).

IsValidIP("What's an IP address?") returns false (correct).

IsValidIP("127") returns true with first version, false with second (correct).

IsValidIP("127.0") returns true with first version, false with second (correct).

Upvotes: 1

Bryan B
Bryan B

Reputation: 4535

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);
        }
    }
}

Upvotes: 6

Steve Wellens
Steve Wellens

Reputation: 20620

If you want to see if the IP address actually exists, you can use the Ping class.

Upvotes: 1

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