using System;
using System.Collections.Generic;
using System.Linq;

public class Test
{
	public static void Main()
	{
		List<string> emails = new List<string>();
		emails.Add("fullname@example.com");
		emails.Add("first_last@example.com");
		emails.Add("first.last@example.com");
		emails.Add("first.middle.last@test.com");
		emails.Add("first.last(comment)@example.com");
		Func<string, bool> dotBeforeAt = delegate(string email) 
		{ 
		    var dotIndex = email.IndexOf(".");
		    return dotIndex > -1 && (dotIndex < email.IndexOf("@"));
		};
		
		foreach(var email in emails.Where(dotBeforeAt)) {
			Console.WriteLine(email);
		}
	}
}