A question about coding choices used here.

[truegoodwill]

Hi @StephenCleary, thank you, I'm really enjoying reading and learning from this code and applying it to my own projects. I have a question which could possibly lead to a small improvement in the BoundActionField ... I'm not sure ... here goes.

You have the following property getter ... I understand perfectly ... it's simply checking what's stored in _field.

public bool IsEmpty => Interlocked.CompareExchange(ref _field, null, null) == null;

But later in the TryUpdateContext method you have the following line of code:

var original = Interlocked.CompareExchange(ref _field, _field, _field);

As far as I can interpret, its purpose is exactly the same as in the property getter ... to grab the value of _field. But here you've used _field, _field for the next two parameters instead of null, null. I don't understand why. It seems "bad" to me, in comparison to supplying nulls. Is there a deliberate reason to this choice, or just randomness?

Thank you.

[truegoodwill]

PS: I've been reading ImmutableInterlocked.cs as well.

Is there anything you would change about your code after reading this? In particular, I noted that this class uses Volatile.Read where you would use Interlocked.CompareExchange(ref _value, null, null) ... is there a difference / comparative advantage?

[StephenCleary]

Yes, it should be using null, null instead of _field, _field. Thanks!

Regarding Volatile vs CompareExchange, they're pretty much equivalent. The CompareExchange technically doesn't have to do a full memory fence like Volatile.Read does, but I believe it does anyway for historical reasons.

[truegoodwill]

Thank you

[StephenCleary]

Fixed in v2.3.0.