Is expression pattern matching for list of lists

[TestMethod]
public void Test() => Assert.IsTrue(FindDifference(new[]{ 1, 2, 3 }, new []{2,4,6}) is [[1,3], [4,6]]);
  

public IList<ILis<int>> FindDifference(int[] nums1, int[] nums2)
        {
            var s1 = new HashSet<int>();
            var s2 = new HashSet<int>();

            var set1 = new HashSet<int>(nums1);
            var set2 = new HashSet<int>(nums2);
            foreach (var n2 in nums2)
                if(!set1.Contains(n2)) s2.Add(n2);
            
            foreach (var n1 in nums1)
                if(!set2.Contains(n1)) s1.Add(n1);
            
            return new List<IList<int>> { s1.ToList(), s2.ToList() };
        }