public void Contains()
        {
            var list = new SortedListReactiveCollectionSource <int>
            {
                1
            };

            list.Contains(1).Should().BeTrue();
            list.Contains(2).Should().BeFalse();
        }
        public void Contains()
        {
            var list = new SortedListReactiveCollectionSource<int>
            {
                1
            };

            list.Contains(1).Should().BeTrue();
            list.Contains(2).Should().BeFalse();
        }