SortedListTKeyTValue

SortedList<TKey, TValue> is a generic collection that stores key-value pairs while maintaining the entries in order of their keys. Keys are required to be unique, while values may be duplicated. The collection exposes fast lookups by key and provides enumeration of the pairs in ascending key order. A custom comparer can be supplied to define a non-default sort order for the keys.

Typical features include access by key through an indexer, and optional access by index to retrieve a KeyValuePair. The collection also exposes separate Keys and Values views, which reflect the current sorted order. Core operations commonly available are Add, Remove, ContainsKey, TryGetValue, Clear, and Count. Attempting to add a pair with a key that already exists generally results in an exception or a rejected operation, depending on the exact API.

In terms of performance, lookups by key are usually logarithmic in time, while insertions and removals that preserve the sorted order can be linear in the number of elements, due to shifting elements to maintain order. Enumeration over the collection iterates in sorted key order and is linear in the number of elements. Memory usage includes storage for the keys and their corresponding values, as well as any overhead for maintaining the sorted structure.

Common use cases include scenarios where a sorted iteration over keys is important, and where frequent key-based access is needed with a predictable iteration order. For alternative behavior with different performance characteristics, see SortedDictionary<TKey, TValue> or Dictionary<TKey, TValue> for unsorted storage or tree-based implementations.