ArrayList Supports Notifications When Items Added or Removed



Public Class ArrayListChangedEventArgs
    Inherits EventArgs

    Public Sub New(list As CairoArrayList, action As ChangeAction)
        Me.List = list
        Me.Action = action
    End Sub

    Public Property List As CairoArrayList
    Public Property Action As ChangeAction

End Class ' ArrayListChangedEventArgs




Public Enum ChangeAction
    Add
    Remoce
End Enum




Public Class CairoArrayList

    Private _list As ArrayList

    Public Sub New()
        Me._list = New ArrayList
    End Sub

    Public ReadOnly Property Items As ArrayList
        Get
            Return Me._list
        End Get
    End Property

    Public Sub Add(value As Object)
        If Me._list IsNot Nothing AndAlso (Not Me._list.Contains(value)) Then
            Me._list.Add(value)
            Me.OnChanged(Me, New ArrayListChangedEventArgs(Me, ChangeAction.Add))
        End If
    End Sub

    Public Sub Remove(value As Object)
        If Me._list IsNot Nothing AndAlso (Me._list.Contains(value)) Then
            Me._list.Remove(value)
            Me.OnChanged(Me, New ArrayListChangedEventArgs(Me, ChangeAction.Remoce))
        End If
    End Sub

    Public Function Contains(key As Object) As Boolean
        Return Me._list IsNot Nothing AndAlso Me._list.Contains(key)
    End Function

    Protected Sub OnChanged(sender As Object, e As ArrayListChangedEventArgs)
        RaiseEvent Changed(Me, e)
    End Sub

    Public Event Changed As EventHandler(Of ArrayListChangedEventArgs)

End Class ' CairoArrayList

Usage:


Define CairoArrayList
Dim list As CairoArrayList = New CairoArrayList

Fill the list with data
list.Add("Cairo")
list.Add("Alex")
list.Add("Aswan")

Add Handler

AddHandler list.Changed, AddressOf OnListChanged

Do something when list changed
    Private Sub Onlistchanged(sender As Object, e As EventArgs)
        ' Do something when items dynamically removed or added to the list
    End Sub


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