Is it possible to lock on a list?

Question

.NET

What is the best way to execute lock
So?

// Создали список на уровне класса
private readonly List<T> _inner;

// Лочимся на объект списка
lock (_inner)
{
    _inner.Clear();
}

Or so?

// Создали список на уровне класса
private readonly List<T> _inner;

// Создали объект для блокировки
private readonly object _lock = new object();

// Лочимся на свой объект
lock (_lock)
{
    _inner.Clear();
}

If the second option, then why? Why is lock on the list itself bad and what is the difference? Why create your own object in this case?

Answer 1

Let's say _inneryou use it in many places, and there is a certain public method that returns it. Then external code can call this method, get the same instance of the object _inner, and put its own lock. So you can accidentally catch a deadlock and hang the application.
Such moments can be very difficult to track down, because the object can be returned indirectly, through an interface, or in some other way. A separate field _lockis just a rule of good taste, it is created for safety: it is very unlikely that someone would think of using it outside of a statement lock, much less returning it from a method.
If you have a small code and you are sure that you know what you are doing - there is no difference.

Answer 2

Why not use ConcurrentBag ?