using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var people = new List<Person>{new Person{GroupId = 1, Name = "Logan", Email = "logan@foo.com"}, new Person{GroupId = 1, Name = "Logan", Email = "logan@foo.com"}, new Person{GroupId = 1, Name = "Logan", Email = "logan@bar.com"}};

        var output = new List<Person>{new Person{GroupId = 1, Name = "Toby", Email = "toby@foo.com"}, new Person{GroupId = 1, Name = "Logan", Email = "logan@bar.com"}};

        foreach (var person in people)

        {

            var e = output.FirstOrDefault(x => x.GroupId == person.GroupId && x.Email == person.Email);

            if (e == null)

            {

                output.Add(person);

            }

        }

​

        Console.WriteLine("If the dedupe logic didn't work, there would be 5 entries listed below:");

        Console.WriteLine("2 entries with \"logan@foo.com\" email addresses");

        Console.WriteLine("and 2 entries with \"logan@bar.com\" email addresses.");

        Console.WriteLine("");

        foreach (var person in output)

        {

            Console.WriteLine("Name: {0}; Email: {1}", person.Name, person.Email);

        }

    }

}

​

public class Person

{

    public int GroupId

    {

        get;

        set;

    }

​

    public string Name

    {

        get;

        set;

    }

​

    public string Email

    {

        get;

        set;

    }

}