using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var text = "aa12,af43,ad46";
    	var pattern = @"^(?:([a-zA-Z]{2}\d{2})(?:,\b|$))+$";
    	var result = Regex.Matches(text, pattern)
    		.Cast<Match>()
    		.Select(x => x.Groups[1].Captures.Cast<Capture>().Select(m => m.Value))
    		.ToList();
        foreach (var list in result)
        	Console.WriteLine(string.Join("; ", list));
	}
}