namespace System.Collections.Immutable { public interface IImmutableDictionary<TKey, TValue> : IReadOnlyDictionary<TKey, TValue>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable { IImmutableDictionary<TKey, TValue> Clear(); IImmutableDictionary<TKey, TValue> Add(TKey key, TValue value); IImmutableDictionary<TKey, TValue> AddRange(IEnumerable<KeyValuePair<TKey, TValue>> pairs); IImmutableDictionary<TKey, TValue> SetItem(TKey key, TValue value); IImmutableDictionary<TKey, TValue> SetItems(IEnumerable<KeyValuePair<TKey, TValue>> items); IImmutableDictionary<TKey, TValue> RemoveRange(IEnumerable<TKey> keys); IImmutableDictionary<TKey, TValue> Remove(TKey key); bool Contains(KeyValuePair<TKey, TValue> pair); bool TryGetKey(TKey equalKey, out TKey actualKey); } }