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Asked: 2026-05-10T23:29:36+00:00

I’m using IPAddress.TryParse() to parse IP addresses. However, it’s a little too permissive (parsing

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I’m using IPAddress.TryParse() to parse IP addresses. However, it’s a little too permissive (parsing ‘1’ returns 0.0.0.1). I’d like to limit the input to dotted octet notation. What’s the best way to do this?

(Note: I’m using .NET 2.0)

Edit

Let me clarify:

I’m writing an app that will scan a range of IPs looking for certain devices (basically a port scanner). When the user enters ‘192.168.0.1’ for the starting address, I want to automatically fill in ‘192.168.0.255’ as the ending address. The problem is that when they type ‘1’, it parses as ‘0.0.0.1’ and the ending address fills in as ‘0.0.0.255’ – which looks goofy.

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1 Answer

  1. If you are interested in parsing the format, then I’d use a regular expression. Here’s a good one (source):

    bool IsDottedDecimalIP(string possibleIP) {     Regex R = New Regex(@'\b(?:\d{1,3}\.){3}\d{1,3}\b');     return R.IsMatch(possibleIP) && Net.IPAddress.TryParse(possibleIP, null); }

    That regex doesn’t catch invalid IPs but does enforce your pattern. The TryParse checks their validity.

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