Implements IEnumerable : IEnumerable « Data Structure « VB.Net

1. VB.Net
2. Data Structure
3. IEnumerable

Implements IEnumerable

 
Imports System
Imports System.Collections

Public Class MainClass
    
    Shared Sub Main()
       Dim currentListBox As New _
           ListBoxTest("Hello", "World")

       'add a few strings
       currentListBox.Add("o")
       currentListBox.Add("s")
       currentListBox.Add("n")
       currentListBox.Add("t")

       'test the access
       Dim subst As String = "Universe"
       currentListBox(1) = subst

       'access all the strings
       Dim s As String
       For Each s In currentListBox
           Console.WriteLine("Value: {0}", s)
       Next

   End Sub

End Class

     Public Class ListBoxTest : Implements IEnumerable
         Private strings(  ) As String
         Private ctr As Integer = 0

         Private Class ListBoxEnumerator
             Implements IEnumerator

             Private currentListBox As ListBoxTest
             Private index As Integer

             Public Sub New(ByVal currentListBox As ListBoxTest)
                 Me.currentListBox = currentListBox
                 index = -1
             End Sub

             Public Function MoveNext(  ) As Boolean _
               Implements IEnumerator.MoveNext
                 index += 1
                 If index >= currentListBox.strings.Length Then
                     Return False
                 Else
                     Return True
                 End If
             End Function

             Public Sub Reset(  ) _
               Implements IEnumerator.Reset
                 index = -1
             End Sub

             Public ReadOnly Property Current(  ) As Object _
             Implements IEnumerator.Current
                 Get
                     Return currentListBox(index)
                 End Get
             End Property
         End Class 

         Public Function GetEnumerator(  ) As IEnumerator _
         Implements IEnumerable.GetEnumerator
             Return New ListBoxEnumerator(Me)
         End Function

         Public Sub New( _
           ByVal ParamArray initialStrings(  ) As String)
             ReDim strings(7)

             Dim s As String
             For Each s In initialStrings
                 strings(ctr) = s
                 ctr += 1
             Next
         End Sub

         Public Sub Add(ByVal theString As String)
             strings(ctr) = theString
             ctr += 1
         End Sub

         Default Public Property Item( _
           ByVal index As Integer) As String
             Get
                 If index < 0 Or index >= strings.Length Then
                     ' handle bad index
                     Exit Property
                 End If
                 Return strings(index)
             End Get
             Set(ByVal Value As String)
                 strings(index) = Value
             End Set
         End Property

         Public Function GetNumEntries(  ) As Integer
             Return ctr
         End Function

     End Class

           
         
  

Related examples in the same category

1.	IEnumerable: array like access
2.	IEnumerable Interface exposes the enumerator, which supports a simple iteration over a non-generic collection.