IDictionary<TKey, TValue>

A dictionary is a natural extension of a set. While a set contains elements (keys) and nothing else, a dictionary stores keys associated with values. As with the set, a dictionary can store a specific key only once.

You are probably already familiar with dictionaries as the standard Delphi implementation has been with us for quite a long time. It is no wonder that the Spring interface, IDictionary<TKey, TValue>, closely mirrors the Delphi version, as shown here in a slightly shortened form:

IDictionary<TKey, TValue> = interface(IMap<TKey, TValue>)
  procedure AddOrSetValue(const key: TKey; const value: TValue);
    deprecated 'Use dict[key] := value instead';
  function Extract(const key: TKey): TValue; 
  function GetValueOrDefault(const key: TKey): TValue;
  function GetValueOrDefault(const key: TKey;
    const defaultValue: TValue): TValue...