using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(\d+)*(\w)\2";
string input = "AA";
Match match = Regex.Match(input, pattern);
// Get the first named group.
Group group1 = match.Groups[1];
Console.WriteLine("Group 1 value: {0}", group1.Success ? group1.Value : "Empty");
// Get the second named group.
Group group2 = match.Groups[2];
Console.WriteLine("Group 2 value: {0}", group2.Success ? group2.Value : "Empty");
// Get a non-existent group.
Group group3 = match.Groups[3];
Console.WriteLine("Group 3 value: {0}", group3.Success ? group2.Value : "Empty");
}
}