1. Basic Collections

2. Collections Basics
Collections are classes that contain a variable number of other objects
Having methods to add and remove objects, to search for objects, to navigate the collection (iterate through the objects in the collection), etc.
Collection Features
Dynamic: whether they can increase the size, all collections in the System.Collections namespace are dynamic
Indexed: whether they are indexed, ArrayList, BitArray, and SortedList classes are indexed
Sorted: whether they are sorted, e.g. SortedList
Access: how they are accessed, by index/key/position

3. Collection Interfaces
IEnumerable and IEnumerator (to navigate the collection)
ICollection, IList, IDictionary
Public Interface IEnumerable
Function GetEnumerator() As IEnumerator
End Interface
Public Interface IEnumerator
ReadOnly Property Current As Object ‘ returns current object
Function MoveNext() As Boolean ‘ false if unsuccessful
Sub Reset() ‘ reset position to 1st
Public Interface ICollection
ReadOnly Property Count As Integer
Sub CopyTo(ByVal array As System.Array, ByVal index As Integer)
ReadOnly Property IsSynchronized As Boolean
ReadOnly Property SyncRoot As Object

4. ArrayList (1) Module Module1 Sub Main()
Dim a As ArrayList = New ArrayList
a.Add("Joe")
a.Add("Jane")
a.Add("Jim")
Dim i As Integer
For i = 0 To a.Count - 1
Console.Out.WriteLine(a.Item(i))
Next
Console.In.ReadLine()
End Sub
End Module

5. ArrayList (2) Module Module1 Sub Main()
Dim a As ArrayList = New ArrayList
a.Add("Joe")
a.Add("Jane")
a.Add("Jim")
Dim e As IEnumerator
e = a.GetEnumerator()
Dim s As String
Do While e.MoveNext()
s = CType(e.Current, String)
Console.Out.WriteLine(s)
Loop
e.Reset()
End Sub
End Module

6. ArrayListExample Sub Main() Dim a As ArrayList = New ArrayList()
a.Add("Joe")
a.Add("Jane")
a.Add("Jim")
Dim sObject As String = "theObject"
a.Insert(2, sObject)
If a.Contains(sObject) Then
Console.Out.WriteLine("a contains sObject")
Dim index As Integer
index = a.IndexOf(sObject)
Console.Out.WriteLine("the index of sObject in a is {0}", index)
End If
If a.IsReadOnly Then
Console.Out.WriteLine("a is read-only")
Else
Console.Out.WriteLine("a is not read-only")
a.RemoveAt(2) ' remove the sObject
Console.Out.WriteLine("a STILL contains sObject")
Console.Out.WriteLine("a does not contains sObject")
End Sub

7. Hashtable A collection of key-value pairs Private Sub ht()
Dim ht As Hashtable = New Hashtable()
Dim p1 As Person = New Person("Joe", #1/1/1961#)
ht.Add(p1.name, p1)
Dim p2 As Person = New Person("Jane", #2/2/1962#)
ht.Add(p2.name, p2)
Dim p3 As Person = New Person("Jim", #3/3/1963#)
ht.Add(p3.name, p3)
Dim p As Person
If ht.Contains("Jim") Then
p = CType(ht.Item("Jim"), Person)
Console.Out.WriteLine("The age of {0} is {1}", p.name, p.getAge())
End If
End Sub

8. More Collections SortedList: HashTableExample and SortedListExample
Queue & Stack: QueueStackExample
Create your own Collections