If the sequence has no elements, LastOrDefault will emit a default value before terminating successfully. This is a subtle but important difference between the LastOrDefault operator and TakeLast(1), which will also complete successfully when the source sequence is empty, but will not emit any values.

Tip

LastOrDefault is one of the simplest and most efficient ways of capturing the end of an observable sequence explicitly as a notification in the workflow. You can use it to react to the termination of a sequence regardless of whether that sequence produces values.