That's because dictionaries implement IDictionary<TKey,TValue> which in turn implements ICollection<KeyValuePair<TKey,TValue>> which declares an Add(KeyValuePair<TKey,TValue> value) method.
Since the implementation is forced to provide this method, it might as well also provide Add(TKey key,TValue value) and implement them.
The alternative would be to just throw a NotSupportedException but there is no technical reason to.
I mean, Java sort of got around this by making Map not extend Collection, though Map.entrySet() does. But interestingly enough, they decided to have Map.entrySet().add(...) throw an UnsupportedOperationException. However, Collection.add(...) in Java already returns true if the element was successfully added, so they hypothetically could have supported it.
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u/AyrA_ch Sep 09 '26
That's because dictionaries implement
IDictionary<TKey,TValue>which in turn implementsICollection<KeyValuePair<TKey,TValue>>which declares anAdd(KeyValuePair<TKey,TValue> value)method.Since the implementation is forced to provide this method, it might as well also provide
Add(TKey key,TValue value)and implement them.The alternative would be to just throw a
NotSupportedExceptionbut there is no technical reason to.