using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var startDateComparer = Comparer<Foo>.Create((a, b) => a.start.CompareTo(b.end));

        SortedSet<Foo> sortedSet = new SortedSet<Foo>(startDateComparer);

        var i1 = new Foo(){ id = "1", start = DateTime.Now, end = DateTime.Now.AddMinutes(1)};

        var i2 = new Foo(){ id = "2", start = DateTime.Now, end = DateTime.Now.AddMinutes(1)};

        sortedSet.Add(i1);

        sortedSet.Add(i2);

        foreach(var item in sortedSet)

        {

            Console.WriteLine(item);

        }

    }

}

​

public class Foo

{

    public string id;

    public DateTime start;

    public DateTime end;

}