Memo

Memoizes async factory calls using with automatic key generation and per-key thundering-herd protection.

Core implementation that handles cache lookup, thundering-herd synchronization, exception caching, and entry creation with the configured policy. Uses a state-passing pattern to avoid closure allocations on the hot path. can be a for efficiency.

null results from the factory are treated as valid cached values for reference types.

Creates with a post-eviction callback that removes the corresponding from to prevent unbounded growth.

Post-eviction callback that cleans up the per-key semaphore from the locks dictionary. Only removes the exact semaphore instance that was captured when the cache entry was created, preserving any newer semaphore created by concurrent callers via GetOrAdd.

Disposes the underlying locks.

Sentinel wrapper stored in the cache when a factory invocation fails, allowing subsequent waiters to short-circuit instead of re-invoking the factory.