Validate whether a string is valid for IP Address or not

Question

As title, I want to validate whether a string is valid for IP Address or not in C#, and I've used

IPAddress.TryParse(value out address)

but it seems not so "Accurate", which means if I enter "500", the address will be "0.0.1.244", so its "Valid".

However, the form I'd like to accept is like "xxx.xxx.xxx.xxx", and each term is less than 256. Is there any API or method could achieve this?

u can create ur custom method.. and u can use this parse method there. — Sandeep Kushwah, May 25 '15 at 10:54
look at this answer for regex http://stackoverflow.com/questions/4890789/regex-for-an-ip-address, also tye using IPAddress.TryParse in http://msdn.microsoft.com/en-us/library/system.net.ipaddress.tryparse.aspx — ahmedsafan86, May 25 '15 at 10:56
Off-topic, but while designing new code, you should account for IPv6, too. — Mihai Caracostea, May 25 '15 at 11:12
not that i have tried anything but couldnt regex be of help here? — Fredrik, May 25 '15 at 11:21
Might be of interest: [IPv4AddressHelper](http://referencesource.microsoft.com/#System/net/System/_IPv4Address.cs,6d6c0ff213882939) — Magnus, May 25 '15 at 11:24

Andrey Korneyev · Accepted Answer · 2015-05-25T11:19:04.280

4

You can pretty straightforward check it: split string to parts separated by dot and ensure it will be exactly four parts having values in range 1...255:

string s = "123.123.123.123";

var parts = s.Split('.');

bool isValid = parts.Length == 4
               && !parts.Any(
                   x =>
                   {
                       int y;
                       return Int32.TryParse(x, out y) && y > 255 || y < 1;
                   });

edited May 25 '15 at 11:19

answered May 25 '15 at 10:57

Andrey Korneyev

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1

Thanks! I think its exactly what I want. – Alanight May 25 '15 at 11:10
on "a12.123.123.123" it will fail, and not return false – Arsen Mkrtchyan May 25 '15 at 11:14
@ArsenMkrtchyan reasonable. It will throw exception though. Have modified the code. – Andrey Korneyev May 25 '15 at 11:18
Also I think condition should be like this Int32.TryParse(x, out y) && y >= 1 && y < 255 – Arsen Mkrtchyan May 25 '15 at 11:32
@ArsenMkrtchyan disagreed. Have a look here: `!parts.Any(` and notice negation operator. – Andrey Korneyev May 25 '15 at 11:33
This fails to validate addresses containing 0. i.e. 192.168.0.1. You would need to check the first and fourth elements independently. – juanlugm Apr 23 '18 at 11:49

score 4 · Answer 2 · edited Jul 28 '20 at 22:06

4

Something like that:

private static Boolean IsIP(String value) {
  if (String.IsNullOrEmpty(value))
    return false;

  var items = value.Split('.');

  if (items.Length != 4)
    return false;

  // Simplest: you may want use, say, NumberStyles.AllowHexSpecifier to allow hex as well
  return items.All(item => byte.TryParse(item, out _));
}

edited Jul 28 '20 at 22:06

Todd Menier

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answered May 25 '15 at 10:59

Dmitry Bychenko

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Frankly, checking each part of address with `Byte.TryParse` is not sufficient, since 0 will be successfully parsed as byte, so this will consider "0.0.1.244" as valid address. – Andrey Korneyev May 25 '15 at 11:08
@AndyKorneyev `0` is valid. Ever heard of `127.0.0.1`? – Magnus May 25 '15 at 11:11

Rahul Tripathi · Answer 3 · 2015-05-25T11:54:16.523

3

If you dont rely on TryParse here is one way to match for xxx.xxx.xxx.xxx

public static bool MyIP(string value)
    {
        var x = value.Split('.');
        if (!(x.Length==4)) 
           return false;

        foreach(var i in x) 
        {
            int q;
            if (!Int32.TryParse(x, out q)||q.ToString().Length.Equals(x.Length) 
                || q < 0 || q > 255) 
            { 
               return false;  
            }

        }

        return true;
    }

edited May 25 '15 at 11:54

answered May 25 '15 at 10:57

Rahul Tripathi

168,305
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what is y? where is it defined or declared – ahmedsafan86 May 25 '15 at 11:02
you still have y.Length, please fix it. – ahmedsafan86 May 25 '15 at 11:53

Matt Brooks · Answer 4 · 2015-05-25T11:33:35.953

2

If you'd rather not do the parsing yourself the NuGet package IPAddressRange will do it for you. It has the advantage of supporting IPv6 addresses as well.

You can check out the source code and documentation here.

edited May 25 '15 at 11:33

answered May 25 '15 at 10:59

Matt Brooks

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1
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score -1 · Answer 5 · answered May 25 '15 at 10:59

-1

string addrString = "192.168.0.1";
IPAddress address;
if (IPAddress.TryParse(addrString, out address)) {
       //Valid IP, with address containing the IP
} else {
       //Invalid IP
}

answered May 25 '15 at 10:59

Omkar Hendre

397
3
12

It's always a good idea to add some explanation to your solution. – PiotrWolkowski May 25 '15 at 13:28
K sir i will keep it in mind and follow next time while answering someone else questions – Omkar Hendre May 26 '15 at 06:44

DermFrench · Answer 6 · 2015-05-26T09:22:16.910

You could try what you are already doing, with a short test before hand to ensure there are the correct number of "."s in the string. https://msdn.microsoft.com/en-us/library/system.net.ipaddress.tryparse.aspx

It will determine if string is valid IPv4 address, this will not work for IPv6:

var stringToCheck = "192.168.1.1";
var countDots = stringToCheck.Split('.').Length - 1;
if (countDots==3)
{
    IPAddress validIpAddress;
    if (IPAddress.TryParse(stringToCheck, out validIpAddress))
    {
        //Valid IP, with validIpAddress containing the IP
        Console.WriteLine("Valid IP");
    }
    else
    {
        //Invalid IP
        Console.WriteLine("Invalid IP");
    }
}
else
{
    // Invalid as no "." in string, not even worth checking
    Console.WriteLine("Invalid IP not correct number Dots");
}

It is indeed returning `true` for `"500"` which is most certainly not a vaild IP address. — molnargab, May 25 '15 at 11:09
I've edited my answer, to check for a "." in the stringToCheck — DermFrench, May 25 '15 at 14:36

Validate whether a string is valid for IP Address or not

6 Answers6