var firstList = new List<Data1>();
var secondList = new List<Data2>();
var sorted = new List<Data2>();
firstList.Each(zz => { sorted.Add(secondList.First(z => z.id_from_firstlist == zz.Id));});

public class Test
{
    public static void Main()
    {

        List<Item1> myList = Test.getmyList();
        List<Item2> externList = Test.getExternList();

        Test.print(myList, "Мой список:");
        Test.print(externList, "Внешний список до сортировки:");

        externList = externList.OrderBy(x => myList.FindIndex(y => x.Name == y.Name)).ToList();

        Test.print(externList, "Внешний список после сортировки:");

    }


    private static List<Item1> getmyList()
    {
        Item1[] items = new Item1[] {
                new Item1 {id = 1, Name = "P1"},
                new Item1 {id = 2, Name = "P2"},
                new Item1 {id = 3, Name = "P3"},
                new Item1 {id = 4, Name = "P4"},
                new Item1 {id = 5, Name = "P5"}
            };
        return items.ToList();
    }

    private static List<Item2> getExternList()
    {
        Item2[] items = new Item2[] {
                new Item2 { Name = "P5"},
                new Item2 { Name = "P4"},
                new Item2 { Name = "P3"},
                new Item2 { Name = "P2"},
                new Item2 { Name = "P1"}
            };
        return items.ToList();
    }

    private static void print<T>(IEnumerable<T> list, string message = "")
    {
        Console.WriteLine(message);
        foreach (var item in list)
        {
            Console.WriteLine(item.ToString());
        }
    }

}

class Item1
{
    public int id { get; set; }
    public string Name { get; set; }

    public override string ToString()
    {
        return Name;
    }
}

class Item2
{
    public string Name { get; set; }
    public override string ToString()
    {
        return Name;
    }
}

class Test
{
    static void Main(string[] args)
    {
        var l1 = new[]
        {
            new C1() { Id = 3, Name = "Иоганн" },
            new C1() { Id = 1, Name = "Ваня" },
            new C1() { Id = 2, Name = "Джонни" }
        };
        var l2 = new[]
        {
            new C2() { Id = 1, Age = 3 },
            new C2() { Id = 3, Age = 331 },
            new C2() { Id = 2, Age = 25 }
        };

        var result =
            from main in l1
            join aux in l2.Select((c2, idx) => new { c2.Id, idx }) on main.Id equals aux.Id
            orderby aux.idx
            select main;

        foreach (var c1 in result)
            Console.WriteLine(c1.Name);
    }
}

class C1
{
    public int Id { get; set; }
    public string Name { get; set; }
}

class C2
{
    public int Id { get; set; }
    public int Age { get; set; }
}