Adds a key-value pair to the collection. The value part of the pair must be a collection of values to associate with the key. If values are already associated with the given key, the new values are added to the ones associated with that key.

public override void Add(
	KeyValuePair<TKey, ICollection<TValue>> item
)

public:
virtual void Add(
	KeyValuePair<TKey, ICollection<TValue>^> item
) override