Difference between lock(this) and a lock on static object

Question

Which of the following two code snippets is better to use?

static readonly object _locker = new object();
lock (_locker)

or

Answer 1

It's almost always preferable to lock on a private readonly object.

The difference is that this is generally visible to outside code, which may take a lock on it, i.e. -

var obj = new YourClass();
lock(obj)
{
    ...
}

...in which case any attempt inside of YourClass to lock (this) would block.