Getting string[] from IPAddressRange

[AndreMantas]

Any better way of doing this?

private string[] GetIPsFromRange(string ipFrom, string ipTo)
{
    var range = new IPAddressRange(IPAddress.Parse(ipFrom), IPAddress.Parse(ipTo));
    var result = new List<string>(255); // could use range.Count here...
    foreach (var ip in range)
    {
        result.Add(ip.ToString());
    }
    return result.ToArray();
}

[jsakamoto]

I prefer this style:

using System.Linq;

private string[] GetIPsFromRange(string ipFrom, string ipTo)
{
    return IPAddressRange.Parse($"{ipFrom} - {ipTo}")
        .Select(ip => ip.ToString())
        .ToArray();
}

[AndreMantas]

Thanks, seems cleaner.

Is IPAddressRange.Parse($"{ipFrom} - {ipTo}") faster than new IPAddressRange(ipFrom, ipTo) ?

[jsakamoto]

I wrote benchmark app. ( code is here.)

• Type1: new IPAddressRange(IPAddress.Parse(ipFrom), IPAddress.Parse(ipTo))
• Type2: IPAddressRange.Parse($"{ipFrom} - {ipTo}")

Condition: Parse 20,000 items x 100 times.
Type 1: Avg.29.12 msec / Min.21 msec / Max.63 msec
Type 2: Avg.164.78 msec / Min.145 msec / Max.296 msec

Type1 seems to be 5~6 times faster than Type2.

Because Type2 (IPAddressRange.Parse($"{ipFrom} - {ipTo}")) is paid for re-formatting and syntax detection ("0.0.0.0-0.0.0.255" style or "0.0.0.0/24" style?) costs.

But please remember that elapsed mill seconds is about parsing 20,000 items, and it took only around 160 msec even Type2.

[AndreMantas]

That was my initial guess as well. Parsing the '{ipFrom} - {ipTo}' should always cause some overhead than receiving the ips in separate variables.

This is really helpful as I'll use this in something that must make as much operations per second as possible, thanks.