What thread synchronization tools have you used in your projects and how did you implement them?

In my projects for thread synchronization in C#, I used several main tools:

• lock — a simple way to lock a critical section, based on a monitor.

private readonly object _lockObj = new object();

lock(_lockObj) {
    // critical section
}

• Mutex — for inter-process synchronization or when a heavier lock is needed.

• SemaphoreSlim — to limit the number of threads executing a certain code simultaneously.

• ManualResetEvent / AutoResetEvent — for signaling between threads.

• Concurrent collections (e.g., ConcurrentDictionary) — for thread-safe work with collections without explicit locking.

Implementation usually boiled down to choosing the appropriate mechanism depending on the task: for simple critical sections — lock, for more complex scenarios — semaphores or events. For example, I used CountdownEvent to wait for the completion of multiple threads.