Chapter 4, Lesson 4 - Using Specialized Collections.

Problem: ArrayList, Sequence Lists, And Dictionary classese can be used to store any object. However often leads to having to cast objects on retrieval from the collection.

Answer: System.Collection.Specialized - collns that are meant to work with specific types of data.

BitArray

• Resizeable colln that stores bools.
• supports std bit-lvl ops.
• constructor - specify size, and then chang size ~ Length property.
• does not support Add() or Remove().
• default value of bits - false.
• set individual bits ~ indexer.
• Can perform ops on 2 BitArray objs of same size.

BitVector32

• Purpose - to aid in manipulating bits in a 32-bit integer.
• not resizeable.

BitVector32 & Bit Masks

• All ops on BitVector32 structure actually change the value of the integer within the structure itself.
• Data property - gets the stored integer.
• CreateMask() - static

BitVector32 & Bit Packing

• taking several smaller numbers & packing them into 1 large number.
• often done to decrease storage of small numbers.
• create sections in structure - CreateSection().

StringCollection

• simple, dynamically sized collection that can only store strings.
• Working with it is virtually identical to using ArrayList.
• no casting on retrieval + will generate compile error it try to insert non-string.

StringDictionary

• Like HashTable - but both key + value are strings.
• keys are case-insensitive by default.

CollectionsUtil - case-insensitive collns of strings

• Creating case-insentitive dictionary collns is so common, there are 2 shortcuts:
• CollectionsUtil.CreateCaseINsensitiveHashtable().
• CollectionsUtil.CreateCaseInsensitiveSortedList().

NameValueCollection Class

• like StringDictionary - keys + values are strings.
• Allows mult. values per key
• can be retrieved by index as well as key.