using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var key1 = new List<int> { 1, 3, 5 };

        var key2 = new List<int> { 2, 4, 6 };

        var key3 = new List<int> { 1, 3, 5 };

        var comparer = new IEnumerableComparer<int>();

        var dictionary = new Dictionary<List<int>, string>(comparer);

        dictionary.Add(key1, "hello");

        dictionary.Add(key2, "world");

        Console.WriteLine(dictionary[key3]);

    }

}

​

public class IEnumerableComparer<T> : IEqualityComparer<IEnumerable<T>>

{

    public bool Equals(IEnumerable<T> x, IEnumerable<T> y)

    {

        return Object.ReferenceEquals(x, y) || (x != null && y != null && x.SequenceEqual(y));

    }

​

    public int GetHashCode(IEnumerable<T> obj)

    {

        unchecked

        {

            return obj.Where(e => e != null).Select(e => e.GetHashCode()).Aggregate(17, (a, b) => 23 * a + b);

        }

    }

}