IPAddress class in Framework 2.0

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Jason - 02 Nov 2006 21:26 GMT

All,

Please note the following:

IPAddress ip = IPAddress.Parse(“10.1.176.10”);

Works fine, as expected, as does:

bool good = IPAddress.TryParse(“10.1.176.10”);

Both return the proper result. HOWEVER…

IPAddress ip = IPAddress.Parse(“10.1.176”);

Also works fine? It creates an IP address object, which when examined became
“10.1.0.176”? WTF?

Note that this also returned true:

bool good = IPAddress.TryParse(“10.1.176”);

Am I simply out of luck until version 3? Is this a known issue? Am I the one
who’s wrong, but just don’t see it? (wouldn't surprise me:-))

For the life of me I can’t understand how TryParse() could return true on an
IP address with only 3 octets?

Please advise….

Thanks,…Jason

Jason Scott Shatzkamer
Director of IT / Ecommerce
Corporate Express
954.379.5415
jason.shatzkamer@cexp.com

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Cowboy (Gregory A. Beamer) - 02 Nov 2006 21:41 GMT

Looks like they missed the "never trust user input" argument. :-)

Signature

Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA
http://gregorybeamer.spaces.live.com

*************************************************
Think outside of the box!
*************************************************

> All,
>
[quoted text clipped - 35 lines]
> 954.379.5415
> jason.shatzkamer@cexp.com

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Turkbear - 02 Nov 2006 22:44 GMT

>All,
>
[quoted text clipped - 32 lines]
>954.379.5415
>jason.shatzkamer@cexp.com

Perhaps the expanation is here:( http://msdn2.microsoft.com/en-gb/library/system.net.ipaddress.parse.aspx )
--------------------------------------------------------
The static Parse method creates an IPAddress instance from an IP address expressed in dotted-quad notation for IPv4 and
in colon-hexadecimal notation for IPv6.

The number of parts (each part is separated by a period) in ipString determines how the IP address is constructed. A one
part address is stored directly in the network address. A two part address, convenient for specifying a class A address,
puts the leading part in the first byte and the trailing part in the right-most three bytes of the network address. A
three part address, convenient for specifying a class B address, puts the first part in the first byte, the second part
in the second byte, and the final part in the right-most two bytes of the network address. For example:

Number of parts and example ipString
IPv4 address for IPAddress

1 -- "65536"
0.0.255.255

2 -- "20.2"
20.0.0.2

2 -- "20.65535"
20.0.255.255

3 -- "128.1.2"
128.1.0.2

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Jason - 02 Nov 2006 23:02 GMT

Nice find...that DOES look a whole lot like my pain :-)

What I do know, however, is that if someone ever called me and I asked them
for their IP address, and they told me "10.1.176", I would say "That is not a
valid IP address."

More so if someone said "65536"...

I guess the real answer, then, is to do the following logic:

string ipString = "10.1.176";
if (IPAddress.TryParse(ipString))
{
IPAddress ip = IPAddress.Parse(ipString);
if (ip.ToString() != ipString)
// Not Valid
else
// Valid
}

That look about right? Seems silly, but works...

Thanks,...J.~

> >All,
> >
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>
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------

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Ben Voigt - 03 Nov 2006 15:14 GMT

> Nice find...that DOES look a whole lot like my pain :-)
>
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>
> That look about right? Seems silly, but works...

It'll reject leading zeros which aren't actually invalid.

Maybe IPAddress.TryParse(ipString) && ipString.Split(new Char[] {
'.' }).Length == 4?

> Thanks,...J.~
>
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>>
>> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------

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IPAddress class in Framework 2.0

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