Can I remove items from a ConcurrentDictionary from within an enumeration loop of that dictionary?

user_15703 0
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So for example:

ConcurrentDictionary<string,Payload> itemCache = GetItems();

foreach(KeyValuePair<string,Payload> kvPair in itemCache)
{
    if(TestItemExpiry(kvPair.Value))
    {   // Remove expired item.
        itemCache.TryRemove(kvPair.Key, out Payload removedItem);
    }
}

Obviously with an ordinary Dictionary<K,V> this will throw an exception, because removing items changes the dictionary's internal state during the life of the enumeration. It's my understanding that this is not the case for a ConcurrentDictionary, as the provided IEnumerable handles internal state changing. Am I understanding this right? Is there a better pattern to use?

parallel-extensions concurrency .net
4 Answers

Just to confirm that the official documentation explicitly states that it is safe:

The enumerator returned from the dictionary is safe to use concurrently with reads and writes to the dictionary, however it does not represent a moment-in-time snapshot of the dictionary. The contents exposed through the enumerator may contain modifications made to the dictionary after GetEnumerator was called.

user_1061590
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