Thread-safe Cached Enumerator - lock with yield

Question

I have a custom \"CachedEnumerable\" class (inspired by Caching IEnumerable) that I need to make thread safe for my asp.net core web app.

Is the following implementa

Answer 1

The access to cache, yes it is thread safe, only one thread per time can read from _cache object.

But in that way you can't assure that all threads gets elements in the same order as they access to GetEnumerator.

Check these two exaples, if the behavior is what you expect, you can use lock in that way.

Example 1:

THREAD1 Calls GetEnumerator

THREAD1 Initialize T current;

THREAD2 Calls GetEnumerator

THREAD2 Initialize T current;

THREAD2 LOCK THREAD

THREAD1 WAIT

THREAD2 read from cache safely _cache[0]

THREAD2 index++

THREAD2 UNLOCK

THREAD1 LOCK

THREAD1 read from cache safely _cache[1]

THREAD1 i++

THREAD1 UNLOCK

THREAD2 yield return current;

THREAD1 yield return current;

---

Example 2:

THREAD2 Initialize T current;

THREAD2 LOCK THREAD

THREAD2 read from cache safely

THREAD2 UNLOCK

THREAD1 Initialize T current;

THREAD1 LOCK THREAD

THREAD1 read from cache safely

THREAD1 UNLOCK

THREAD1 yield return current;

THREAD2 yield return current;