What is a ConcurrentDictionary<TKey, TValue> in C#?

Short answer: ConcurrentDictionary<TKey, TValue> is a thread-safe dictionary designed for concurrent access by multiple threads without needing external synchronization (locks). Supports atomic operations like adding, updating, and removing items. Useful in multi-threaded scenarios where data integrity and performance are critical.

Example code

ConcurrentDictionary<int, string> concurrentDict = new ConcurrentDictionary<int, string>(); concurrentDict.TryAdd(1, "One"); concurrentDict.TryUpdate(1, "Uno", "One");

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1. Define — one clear sentence (the short answer above).
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3. Trade-off — when you would not use it.