Question

I have the following code:

List<List<int>> list = new List<List<int>>();
list.Add(new List<int> { 0, 1 });

if (list.Contains(new List<int> { 0, 1 }))      // false
  ...

I’m trying to check whether the list contains {0,1}, but the condition is false (I don’t know why, maybe because the ‘new’ keyword).
If this is not the proper way, I’d like to know how to check that.

Thanks!

Answer 1

List<T>.Contains calls the Equals() method to compare objects.
Since the inner List<T> doesn’t override Equals, you get reference equality.

You can fix this by creating a custom IEqualityComparer<List<T>> that compares by value and passing it to Contains().

You can also just use LINQ:

if (list.Any(o => o.SequenceEqual(new[] { 0, 1 }))