See Also: IDictionary Members
Each key-value pair must have a unique non-null key, but the value of an association can be any object reference, including a null reference. The IDictionary interface allows the contained keys and values to be enumerated, but it does not imply any particular sort order.
IDictionary implementations fall into three categories: read-only, fixed-size, variable-size. A read-only implementation cannot be modified. A fixed-size implementation does not allow the addition or removal of elements, but it allows the modification of existing elements. A variable-size implementation allows the addition, removal and modification of elements.