[RESOLVED] [2005] Generics (Of T)
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Thread: [RESOLVED] [2005] Generics (Of T)

  1. #1
    Join Date
    Sep 2005
    Posts
    59

    [RESOLVED] [2005] Generics (Of T)

    Hello everyone. I'm struggling to get my head around generics, so I decided to make an example.

    I added a new class and typed :
    Code:
    Public Class MyGenericList(Of T)
        Implements ICollection
        Implements IEnumerable
    
        Public InnerList As ArrayList = New ArrayList()
    
        Public Sub Add(ByVal val As T)
            InnerList.Add(val)
        End Sub
    
        Default Public ReadOnly Property Item(ByVal index As Integer) As T
            Get
                Return CType(InnerList(index), T)
            End Get
        End Property
    End Class
    As I understand, this will enable me to add Integers, Strings or whatever separately to this list, so this is what I did inside my Form
    Code:
    Public Class Form1
        Private IntList As New MyGenericList(Of Integer)()
        Private StringList As New MyGenericList(Of String)()
    
    
        Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
            IntList.Add(0)
            IntList.Add(1)
            IntList.Add(2)
            IntList.Add(3)
            IntList.Add(4)
    
            StringList.Add("Zero")
            StringList.Add("One")
            StringList.Add("Two")
            StringList.Add("Three")
            StringList.Add("Four")
        End Sub
    
        Public Sub Display(Of T)(ByVal list As MyGenericList(Of T))
            For Each obj As T In New List(Of T)()
                Console.WriteLine(obj.ToString)
            Next
        End Sub
    
        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            Dim list As New MyGenericList(Of Integer)
            Display(Of Integer)(list)
    
        End Sub
    End Class
    But nothing gets outputted to the Output window.

    I'd just like to know how I can enumerate the items in my generic list. Can anyone help?

  2. #2
    Join Date
    Sep 2005
    Posts
    59

    Re: [2005] Generics (Of T)

    Don't worry, I fixed it myself. This is what I did:

    Generic Class:
    Code:
    Public Class MyGenericList(Of T)
        Inherits CollectionBase
        Implements ICollection
    
        Public Function Add(ByVal value As T) ' As T
            Return List.Add(value)
        End Function
    
        Public Sub Remove(ByVal value As T)
            List.Remove(value)
        End Sub
    
        Public ReadOnly Property Item(ByVal index As Integer) As T
            Get
                Return CType(List.Item(index), T)
            End Get
        End Property
    
    End Class
    Form:
    Code:
    Public Class Form1
        Private IntList As New MyGenericList(Of Integer)()
        Private StringList As New MyGenericList(Of String)()
        Private ButClicked As Integer
    
        Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    
            IntList.Add(0)
            IntList.Add(1)
            IntList.Add(2)
            IntList.Add(3)
            IntList.Add(4)
    
            StringList.Add("Zero")
            StringList.Add("One")
            StringList.Add("Two")
            StringList.Add("Three")
            StringList.Add("Four")
    
        End Sub
    
        Public Sub Display(Of T)(ByVal list As MyGenericList(Of T))
            Select Case ButClicked
                Case 0
                    For Each obj As T In IntList
                        Console.WriteLine(obj.ToString)
                    Next
                Case 1
                    For Each obj As T In StringList
                        Console.WriteLine(obj.ToString)
                    Next
            End Select
    
        End Sub
    
        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            ButClicked = 0
            Dim list As MyGenericList(Of Integer)
            Display(Of Integer)(list)
        End Sub
    
        Private Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
            ButClicked = 1
            Dim list As MyGenericList(Of String)
            Display(Of String)(list)
        End Sub
    End Class
    Last edited by GrimmReaper; December 30th, 2008 at 03:52 AM.

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