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I'm noticing that GetOrAdd() always executes the factory delegate, even when the value exists in the dictionary. For example: class Program { private static ConcurrentDictionary<string, string> _cache = new ConcurrentDictionary<string, string>(); static void Main(string[] args) { string value; value = GetValueFromCache("A"); // cache is empty, CacheValueFactory executes, A is added value = GetValueFromCache("A"); // cache contains A, CacheValueFactory executes value = GetValueFromCache("C"); // cache contains A, CacheValueFactory, C is added value = GetValueFromCache("A"); // cache contains A and C, CacheValueFactory executes } private static string GetValueFromCache(string key) { string val = _cache.GetOrAdd(key, CacheValueFactory(key)); return val; } private static string CacheValueFactory(string key) { if (key == "A") return "Apple"; else if (key == "B") return "Banana"; else if (key == "C") return "Cherry"; return null; } } Upon the first call to GetValueFromCache("A"), the cache is empty and A:Apple is added. Stepping in with the debugger, I noticed that on the second and third calls to GetValueFromCache("A"), the CacheValueFactory() method always executes. Is this expected? I would've thought that the delegate method wouldn't execute if the key exists in the dictionary.

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