How to distinguish a regular dictionary from the thread-safe implementation of ConcurrentDictionary in C#?

A regular dictionary (for example, Dictionary<TKey, TValue>) in C# does not guarantee safety when accessed concurrently from multiple threads. If multiple threads read and write to such a dictionary simultaneously, a race condition may occur, leading to errors or data corruption.

ConcurrentDictionary<TKey, TValue> is a thread-safe implementation of a dictionary that allows safe read and write operations from multiple threads without additional synchronization.

Main differences:

• Thread safety: ConcurrentDictionary uses internal locking mechanisms and optimizations for safe access.
• Methods for atomic operations: such as TryAdd, TryUpdate, AddOrUpdate, which perform add or update operations atomically.
• Performance: under multithreaded access, ConcurrentDictionary generally performs better than a regular dictionary with external locking.

Example of using ConcurrentDictionary:

using System.Collections.Concurrent;

var dict = new ConcurrentDictionary<int, string>();
dict.TryAdd(1, "one");
dict.AddOrUpdate(1, "uno", (key, oldValue) => "uno");

In a regular Dictionary, external locks (lock) are needed for thread safety, which complicates the code and can reduce performance.