ReadOnlyDictionary<TKey, TValue>
public class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, IReadOnlyDictionary<TKey, TValue>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IDictionary, ICollection, IEnumerable
public sealed class KeyCollection<TKey, TValue> : ICollection<TKey>, IReadOnlyCollection<TKey>, IEnumerable<TKey>, ICollection, IEnumerable
public sealed class ValueCollection<TKey, TValue> : ICollection<TValue>, IReadOnlyCollection<TValue>, IEnumerable<TValue>, ICollection, IEnumerable