using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<SomeEventObject> EventList = new List<SomeEventObject>();

        DateTime now = DateTime.Now;

        SomeEventObject event1 = new SomeEventObject("1", new DateTime(now.Year, now.Month, now.Day, 10, 0, 0), new DateTime(now.Year, now.Month, now.Day, 10, 5, 0));

        EventList.Add(event1);

        SomeEventObject event2 = new SomeEventObject("2", new DateTime(now.Year, now.Month, now.Day, 10, 5, 0), new DateTime(now.Year, now.Month, now.Day, 10, 10, 0));

        EventList.Add(event2);

        List<SomeEventObject> overlappingEvents = EventList.Where (e => 

                    EventList.Any (ev => e.id != ev.id && ev.StartDate <= e.EndDate && ev.EndDate >= e.StartDate)).ToList();

        foreach(SomeEventObject eventItem in overlappingEvents){

            Console.WriteLine(eventItem.id);

        }

    }

}

​

public class SomeEventObject

{

    public string id

    {

        get;

        set;

    }

​

    public DateTime StartDate

    {

        get;

        set;

    }

​

    public DateTime EndDate

    {

        get;

        set;

    }

​

    public SomeEventObject(string id, DateTime startDate, DateTime endDate)

    {

        this.id = id;

        this.StartDate = startDate;

        this.EndDate = endDate;

    }

}