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Visual Basic .NETSORGENTI - VARIE - COSTRUIRE UNA LISTBOX IMPLEMENTANDO 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 |