How do you parse an IP address string to a uint value in C#?

Question

I'm writing C# code that uses the windows IP Helper API. One of the functions I'm trying to call is "GetBestInterface" that takes a 'uint' representation of an IP. What I need is to parse a textual representation of the IP to create the 'uint' representation.

I've found some examples via Google, like this one or this one, but I'm pretty sure there should be a standard way to achieve this with .NET. Only problem is, I can't find this standard way. IPAddress.Parse seems to be in the right direction, but it doesn't supply any way of getting a 'uint' representation...

There is also a way of doing this using IP Helper, using the ParseNetworkString, but again, I'd rather use .NET - I believe the less I rely on pInvoke the better.

So, anyone knows of a standard way to do this in .NET?

possible duplicate of How to convert an IPv4 address into a integer in C# as nt. pointed out? — Deanna
– Deanna, Commented Aug 10, 2012 at 8:39
You shouldn't be relying on the fact that an IP address can fit i a 32-bit number. Some IP addresses are 128-bit. And by hard-coding a dependency on 32-bit addresses: you limit how useful your system is. — Ian Boyd
– Ian Boyd, Commented Dec 8, 2021 at 2:51

Christo · Accepted Answer · 2009-02-16 13:34:14Z

18

Shouldn't it be:

var ipAddress = IPAddress.Parse("some.ip.address");
var ipBytes = ipAddress.GetAddressBytes();
var ip = (uint)ipBytes [0] << 24;
ip += (uint)ipBytes [1] << 16;
ip += (uint)ipBytes [2] <<8;
ip += (uint)ipBytes [3];

?

answered Feb 16, 2009 at 13:34

Christo

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Community · Accepted Answer · 2017-05-23 12:13:34Z

16

var ipuint32 = BitConverter.ToUInt32(IPAddress.Parse("some.ip.address.ipv4").GetAddressBytes(), 0);`

This solution is easier to read than manual bit shifting.

See How to convert an IPv4 address into a integer in C#?

edited May 23, 2017 at 12:13

CommunityBot

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answered Aug 31, 2008 at 23:01

nimish

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2 Comments

mjv Over a year ago

BitConvertor.ToUINt32() takes two parameters (see msdn.microsoft.com/en-us/library/…)

Popeye Over a year ago

Whoever tried to edit this answer please don't try editing code, even if incorrect because of typo just add a comment to inform the user who the answer belongs to, and don't go deleting the rest of the answer to just say why you did it.

aku · Accepted Answer · 2008-08-31 22:30:23Z

13

MSDN says that IPAddress.Address property (which returns numeric representation of IP address) is obsolete and you should use GetAddressBytes method.

You can convert IP address to numeric value using following code:

var ipAddress = IPAddress.Parse("some.ip.address");
var ipBytes = ipAddress.GetAddressBytes();
var ip = (uint)ipBytes [3] << 24;
ip += (uint)ipBytes [2] << 16;
ip += (uint)ipBytes [1] <<8;
ip += (uint)ipBytes [0];

EDIT:
As other commenters noticed above-mentioned code is for IPv4 addresses only. IPv6 address is 128 bits long so it's impossible to convert it to 'uint' as question's author wanted.

edited Aug 31, 2008 at 22:30

answered Aug 31, 2008 at 12:55

aku

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2 Comments

Andrei Rînea Over a year ago

Are you sure about the four indices' order? it seems to me that byte with index 0 should be shifted 24 bits and not the one with index 3..

Janis Veinbergs Over a year ago

Or instead of last 4 lines, use: BitConverter.ToUInt32(ipBytes, 0) See this fiddle on how to convert it to use network byte order that increments naturally as IP addresses goes: dotnetfiddle.net/eZguXl

Corin Blaikie · Accepted Answer · 2008-08-31 14:13:11Z

5

Also you should remember that IPv4 and IPv6 are different lengths.

answered Aug 31, 2008 at 14:13

Corin Blaikie

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Comments

Nick · Accepted Answer · 2019-09-18 21:33:25Z

2

Correct solution that observes Endianness:

var ipBytes = ip.GetAddressBytes();
ulong ip = 0;
if (BitConverter.IsLittleEndian)
{
    ip = (uint) ipBytes[0] << 24;
    ip += (uint) ipBytes[1] << 16;
    ip += (uint) ipBytes[2] << 8;
    ip += (uint) ipBytes[3];
}
else
{
    ip = (uint)ipBytes [3] << 24;
    ip += (uint)ipBytes [2] << 16;
    ip += (uint)ipBytes [1] <<8;
    ip += (uint)ipBytes [0];
}

edited Sep 18, 2019 at 21:33

answered Sep 17, 2019 at 19:06

Nick

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Comments

Dmitry Shechtman · Accepted Answer · 2008-08-31 12:59:35Z

1

Byte arithmetic is discouraged, as it relies on all IPs being 4-octet ones.

answered Aug 31, 2008 at 12:59

Dmitry Shechtman

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Comments

qasali · Accepted Answer · 2010-10-10 10:59:33Z

1

System.Net.IPAddress ipAddress = System.Net.IPAddress.Parse("192.168.1.1");

byte[] bytes = ipAddress.GetAddressBytes();
for (int i = 0; i < bytes.Length ; i++)
       Console.WriteLine(bytes[i]);

Output will be 192 168 1 1

answered Oct 10, 2010 at 10:59

qasali

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Comments

Pavel Samoylenko · Accepted Answer · 2018-05-05 10:50:59Z

Complete solution:

public static uint IpStringToUint(string ipString)
{
    var ipAddress = IPAddress.Parse(ipString);
    var ipBytes = ipAddress.GetAddressBytes();
    var ip = (uint)ipBytes [0] << 24;
    ip += (uint)ipBytes [1] << 16;
    ip += (uint)ipBytes [2] <<8;
    ip += (uint)ipBytes [3];
    return ip;
}

public static string IpUintToString(uint ipUint)
{
    var ipBytes = BitConverter.GetBytes(ipUint);
    var ipBytesRevert = new byte[4];
    ipBytesRevert[0] = ipBytes[3];
    ipBytesRevert[1] = ipBytes[2];
    ipBytesRevert[2] = ipBytes[1];
    ipBytesRevert[3] = ipBytes[0];
    return new IPAddress(ipBytesRevert).ToString();
}

Reverse order of bytes:

public static uint IpStringToUint(string ipString)
{
    return BitConverter.ToUInt32(IPAddress.Parse(ipString).GetAddressBytes(), 0);
}

public static string IpUintToString(uint ipUint)
{
    return new IPAddress(BitConverter.GetBytes(ipUint)).ToString();
}

You can test here:

https://www.browserling.com/tools/dec-to-ip

http://www.smartconversion.com/unit_conversion/IP_Address_Converter.aspx

http://www.silisoftware.com/tools/ipconverter.php

Jeremy Caney · Accepted Answer · 2025-05-08 00:03:01Z

Most of the answers here are pretty old, and since then C# has been updated with the ability to allocate memory on stack instead of heap. Using stackalloc allows us to write more efficient code that does not allocate any memory which needs to be cleaned up afterwards.

public static uint GetIPV4AddressUint(IPAddress ipAddr)
{
    if (ipAddr.AddressFamily is not AddressFamily.InterNetwork) throw new InvalidOperationException("GetIPV4Adress supports only ipv4 addresses");
    Span<byte> addrBytes = stackalloc byte[4];
    if (!ipAddr.TryWriteBytes(addrBytes, out int _)) throw new InvalidDataException("Unable to get ip address bytes");
    return ((uint)addrBytes[3] << 24) + ((uint)addrBytes[2] << 16) + ((uint)addrBytes[1] << 8) + addrBytes[0];
}

Benchmark (using BenchmarkDotNet, .NET6)


[Benchmark]
public uint GetIPV4AddressUint_Stackalloc()
{
    IPAddress ipAddr = IPAddress.Any;
    if (ipAddr.AddressFamily is not AddressFamily.InterNetwork) throw new InvalidOperationException("GetIPV4Adress supports only ipv4 addresses");
    Span<byte> addrBytes = stackalloc byte[4];
    if (!ipAddr.TryWriteBytes(addrBytes, out int _)) throw new InvalidDataException("Unable to get ip address bytes");
    return ((uint)addrBytes[3] << 24) + ((uint)addrBytes[2] << 16) + ((uint)addrBytes[1] << 8) + addrBytes[0];
}

[Benchmark]
public uint GetIPV4AddressUint_ByteArray_TryWriteBytes()
{
    IPAddress ipAddr = IPAddress.Any;
    if (ipAddr.AddressFamily is not AddressFamily.InterNetwork) throw new InvalidOperationException("GetIPV4Adress supports only ipv4 addresses");
    byte[] addrBytes = new byte[4];
    if (!ipAddr.TryWriteBytes(addrBytes, out int _)) throw new InvalidDataException("Unable to get ip address bytes");
    return ((uint)addrBytes[3] << 24) + ((uint)addrBytes[2] << 16) + ((uint)addrBytes[1] << 8) + addrBytes[0];
}

[Benchmark]
public uint GetIPV4AddressUint_ByteArray_GetAddressBytes()
{
    IPAddress ipAddr = IPAddress.Any;
    if (ipAddr.AddressFamily is not AddressFamily.InterNetwork) throw new InvalidOperationException("GetIPV4Adress supports only ipv4 addresses");
    byte[] addrBytes = ipAddr.GetAddressBytes();
    return ((uint)addrBytes[3] << 24) + ((uint)addrBytes[2] << 16) + ((uint)addrBytes[1] << 8) + addrBytes[0];
}

Benchmark results

Method	Mean	Error	StdDev	Median	Allocated
GetIPV4AddressUint_Stackalloc	5.096 ns	0.1577 ns	0.4576 ns	5.119 ns	-
GetIPV4AddressUint_ByteArray_TryWriteBytes	9.663 ns	0.2761 ns	0.7879 ns	9.403 ns	32 B
GetIPV4AddressUint_ByteArray_GetAddressBytes	7.885 ns	0.1756 ns	0.1643 ns	7.877 ns	32 B

Andrei Rînea · Accepted Answer · 2008-08-31 12:56:19Z

0

I have never found a clean solution (i.e.: a class / method in the .NET Framework) for this problem. I guess it just isn't available except the solutions / examples you provided or Aku's example. :(

answered Aug 31, 2008 at 12:56

Andrei Rînea

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