using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^
(?(DEFINE)(?<part>(?:xn--)?[a-z\d](?:[a-z\d-]*[a-z\d])?))
(?(DEFINE)(?<subpart>(?:xn--)?[a-z\d_](?:[a-z\d_-]*[a-z\d])?))
(?:(?&subpart)\.)*
(?&part)
(?:\.[a-z]+|\.xn--[a-z\d]+){1,2}
$";
string input = @"www.foo.bar.baz
www.foo.bar
foo.bar.baz
foo.bar
foo
xn--tst-qla.de
xn--tst-qla.xn--tst-qla.de
xn--tst-qla.xn--tstqla
ASPMX.L.GOOGLE.COM
";
RegexOptions options = RegexOptions.IgnorePatternWhitespace | RegexOptions.IgnoreCase | RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx