C#: How do you work with generics?

1public class Repository<T> where T : class
2{
3    private readonly List<T> _items = new();
4
5    public void Add(T item) => _items.Add(item);
6    public T GetById(int id) => _items[id];
7}

1public T Max<T>(T a, T b) where T : IComparable<T>
2{
3    return a.CompareTo(b) > 0 ? a : b;
4}