Returns a read-only view onto a collection. The returned ICollection<T> interface only allows operations that do not change the collection: GetEnumerator, Contains, CopyTo, Count. The ReadOnly property returns false, indicating that the collection is read-only. All other methods on the interface throw a NotSupportedException.

Returns a read-only view onto a dictionary. The returned IDictionary<TKey,TValue> interface only allows operations that do not change the dictionary. The IsReadOnly property returns true, indicating that the dictionary is read-only. All other methods on the interface throw a NotSupportedException.

Returns a read-only view onto a list. The returned IList<T> interface only allows operations that do not change the list: GetEnumerator, Contains, CopyTo, Count, IndexOf, and the get accessor of the indexer. The IsReadOnly property returns true, indicating that the list is read-only. All other methods on the interface throw a NotSupportedException.