Thread synchronization is essential to ensure that multiple threads access shared resources safely and predictably. In C#, several synchronization techniques are available, each suited to different scenarios. Here's a structured overview:

Types of Thread Synchronization Techniques in C#

1. Locking Mechanisms

• lock statement: Simplifies mutual exclusion using Monitor internally.
• Monitor.Enter / Monitor.Exit: Offers fine-grained control over locking.
• Mutex: Enables synchronization across processes.
• SpinLock: Lightweight lock for short critical sections.
• ReaderWriterLockSlim: Optimized for frequent reads and rare writes.

2. Signaling Constructs

• AutoResetEvent: Resets automatically after releasing one thread.
• ManualResetEvent: Stays signaled until manually reset.
• CountdownEvent: Waits for a set number of signals.
• Barrier: Synchronizes threads at a common point.
• Semaphore / SemaphoreSlim: Limits concurrent access to resources.

3. Volatile and Atomic Operations

• volatile keyword: Ensures visibility of variable changes across threads.
• Interlocked class: Provides atomic operations like increment and exchange.

4. Thread-Safe Collections

• ConcurrentDictionary
• ConcurrentQueue
• ConcurrentBag: Built-in thread-safe collections for concurrent scenarios.

5. Task-Based Synchronization

• async/await with SemaphoreSlim: Controls concurrency in async code.
• CancellationToken: Coordinates cancellation across threads or tasks.

6. Immutable Data Structures

• Immutable objects eliminate the need for synchronization.

7. ThreadLocal Storage

• ThreadLocal<T>: Provides thread-specific data to avoid shared state.

🔍 Thread Synchronization Primitives in C#

clear comparison of Mutex, Monitor, and Semaphore in C#—tailored for architectural decision-making and team enablement:

Feature	Monitor	Mutex	Semaphore
Scope	Intra-process only	Cross-process capable	Intra- or cross-process
Ownership	Thread-based	Thread-based	Not tied to thread ownership
Lock Count	Single thread at a time	Single thread at a time	Multiple threads (configurable count)
Performance	Lightweight	Heavier (kernel-level)	Moderate
Use Case	Protect critical sections in same app	Synchronize across apps/processes	Limit concurrent access (e.g., throttling)
API Example	Monitor.Enter(obj) / lock(obj)	mutex.WaitOne() / mutex.Release()	semaphore.WaitOne() / semaphore.Release()
Named Support	❌	✅ (Named Mutex for inter-process)	✅ (Named Semaphore)
Exception Safety	lock is safer than raw Monitor	Must manually release	Must manually release

🧠 When to Use What

• Use Monitor or lock for simple thread synchronization within a single process. It’s fast and easy.
• Use Mutex when you need to coordinate access across multiple processes (e.g., ensuring only one instance of an app runs).
• Use Semaphore when you want to allow a limited number of threads to access a resource concurrently (e.g., throttling access to a database or service).