Will TransformBlock<TInput,TOutput>.TryReceiveAll(IList<TOutput>) return true when if and only if all the element(s) received?

Question

Previously pasted picture is the official definition. But I am still confused. Does it return true if and only if all the element(s) received?

Answer 1

Let's look at the documentation

TransformBlock<TInput,TOutput>.TryReceiveAll(IList<TOutput>) Method

Returns

true if one or more items could be received; otherwise, false.

It says it returns true if it has received at least 1 item

Let's make sure:

...

while (_messages.TryDequeue(out item)) 
    tmpList.Add(item);

countReceived = tmpList.Count;

...

if (countReceived > 0)
{
    // Notify the owner block that our count has decreased
    if (_itemsRemovedAction != null)
    {
        int count = _itemCountingFunc != null ? _itemCountingFunc(_owningSource, default(TOutput)!, items) : countReceived;
        _itemsRemovedAction(_owningSource, count);
    }
    return true;
}
else return false;

Yup, documentation is correct...

Does it return true if and only if all the element(s) received?

I guess the answer to this revolves around what you class as all...

What is buffered internally awaiting dispatch (queued), and what is in your pipeline may be 2 completely different things. TryReceiveAll will only return queued items. Items that haven't been queued (ergo not available) or otherwise held-up in other blocks (which you may consider all) is not classed as received.

For instance, you could have 10 items in flight in your entire pipeline, only 2 has hit the transform block and awaiting dispatch. TryReceiveAll will return those 2 available items, and return true.