IPAddressRange Class Library 
This library allows you to parse range of IP address string such as "192.168.0.0/24" and "192.168.0.0/255.255.255.0" and "192.168.0.0-192.168.0.255", and can contains check. This library supports both IPv4 and IPv6.
Example
using NetTools;
...
// rangeA.Begin is "192.168.0.0", and rangeA.End is "192.168.0.255".
var rangeA = IPAddressRange.Parse("192.168.0.0/255.255.255.0");
rangeA.Contains(IPAddress.Parse("192.168.0.34")); // is True.
rangeA.Contains(IPAddress.Parse("192.168.10.1")); // is False.
rangeA.ToCidrString(); // is 192.168.0.0/24
// rangeB.Begin is "192.168.0.10", and rangeB.End is "192.168.10.20".
var rangeB1 = IPAddressRange.Parse("192.168.0.10 - 192.168.10.20");
rangeB1.Contains(IPAddress.Parse("192.168.3.45")); // is True.
rangeB1.Contains(IPAddress.Parse("192.168.0.9")); // is False.
// Support shortcut range description.
// ("192.168.10.10-20" means range of begin:192.168.10.10 to end:192.168.10.20.)
var rangeB2 = IPAddressRange.Parse("192.168.10.10-20");
// Support CIDR expression and IPv6.
var rangeC = IPAddressRange.Parse("fe80::/10");
rangeC.Contains(IPAddress.Parse("fe80::d503:4ee:3882:c586%3")); // is True.
rangeC.Contains(IPAddress.Parse("::1")); // is False.
// "Contains()" method also support IPAddressRange argument.
var rangeD1 = IPAddressRange.Parse("192.168.0.0/16");
var rangeD2 = IPAddressRange.Parse("192.168.10.0/24");
rangeD1.Contains(rangeD2); // is True.
// IEnumerable<IPAddress> support, it's lazy evaluation.
foreach (var ip in IPAddressRange.Parse("192.168.0.1/23"))
{
Console.WriteLine(ip);
}
// You can use LINQ via "AsEnumerable()" method.
var longValues = IPAddressRange.Parse("192.168.0.1/23")
.AsEnumerable()
.Select(ip => BitConvert.ToInt32(ip.GetAddressBytes(), 0))
.Select(adr => adr.ToString("X8"));
Console.WriteLine(string.Join(",", longValues);
// Constructors from IPAddress objects.
var ipBegin = IPAddress.Parse("192.168.0.1");
var ipEnd = IPAddress.Parse("192.168.0.128");
var ipSubnet = IPAddress.Parse("255.255.255.0");
var rangeE = new IPAddressRange(); // This means "0.0.0.0/0".
var rangeF = new IPAddressRange(ipBegin, ipEnd);
var rangeG = new IPAddressRange(ipBegin, maskLength: 24);
var rangeH = new IPAddressRange(ipBegin, IPAddressRange.SubnetMaskLength(ipSubnet));
// Calculates Cidr subnets
var rangeI = IPAddressRange.Parse("192.168.0.0-192.168.0.254");
rangeI.ToCidrString(); // is 192.168.0.0/24Release Note
The release notes is here.