Gets a value indicating whether the IDictionary object has a fixed size.
true if the current instance has a fixed size; otherwise, false.
A collection with a fixed size does not allow the addition or removal of elements after the collection is created, but does allow the modification of existing elements.
A collection with a fixed size is simply a collection with a wrapper that prevents adding and removing elements; therefore, if changes are made to the underlying collection, including the addition or removal of elements, the fixed-size collection reflects those changes.