Visual basic Webform ASP.net

Question

Not sure why the labels are not continuously switching.

I break-pointed it and it shows the counter resets everytime and so it should just be continuously swapping through the numbers but it doesn't seem to be working

Thanks!

Public Class WebForm2 Inherits System.Web.UI.Page

Dim d As Integer() = {0, 1, 2, 3, 4}
Dim counter As Integer
Public Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        Label1.Text = d(0)
        Label2.Text = d(1)
        Label3.Text = d(2)
        Label4.Text = d(3)
        Label5.Text = d(4)
    End If
End Sub

Public Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    Dim hold As Integer
    counter = 0
    hold = d(0)
    Do While counter < 4
        d(counter) = d(counter + 1)
        counter += 1
    Loop
    Label1.Text = d(0)
    Label2.Text = d(1)
    Label3.Text = d(2)
    Label4.Text = d(3)
    Label5.Text = hold
End Sub

Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
    Dim hold As Integer
    counter = 0
    hold = d(0)
    Do While counter < 4
        d(counter) = d(counter + 1)
        counter += 1
    Loop

    Label1.Text = d(0)
    Label2.Text = d(1)
    Label3.Text = d(2)
    Label4.Text = d(3)
    Label5.Text = hold
End Sub

End Class

Answer 1

I am not familiar with vb.net but I've created asp.net pages before so I am taking an educated guess here^^

When clicking the button a postback happens and the whole page gets reloaded and the array d is declared again.

The values you store in your array are lost after the Post-Back. For keeping data you could use Session or ViewState variables:

Session

ViewState

As I said this is for asp.net but it might help anyways.

Edit: I still think the data is somewhere lost in this d-array... What if you just leave out the array and have your button_Click event like this:

        String temp = Label1.Text;

        Label1.Text = Label2.Text;
        Label2.Text = Label3.Text;
        Label3.Text = Label4.Text;
        Label4.Text = Label5.Text;
        Label5.Text = temp;

Answer 2

Your array named d (is there a better name for this?) is being re-declared on every page-load (as it seems like it should be).

The problem is that you're not persisting the adjusted array values each page load. Instead, you're starting from scratch each time as others have suggested.

See the following URL for a lot of useful information about persisting state information in a web-forms application.

http://msdn.microsoft.com/en-us/library/vstudio/z1hkazw7(v=vs.100).aspx

As far as your code, you can try something along these lines to persist the values from the current array while setting it up for the next load.

Public Class WebForm2 Inherits System.Web.UI.Page

    Private _dValues As Integer(19)
    Private _currentValues As Integer(19)
    Private _newValues As Integer(19)
    Private _startIndex As Integer

    Public Sub New()
        _dValues = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19}
        _startIndex = 0
    End Sub

    Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
        If Page.IsPostBack Then 'Load values from form
            For i As Integer = 0 To _currentValues.Length - 1 Step 1
                _currentValues(i) = Request.Form(String.Concat("Hidden", i))
            Next
            _startIndex = Request.Form("StartIndex")
        Else
            _currentValues = _dValues 'First time around
        End If
        Dim position As Integer = _startIndex
        For i As Integer = 0 To _currentvalues.Length - 1 Step 1
            If position >= _newValues.Length Then
                position = 0
            End If
            'Assign the current position in the new array equal to the current sequential value in the previous array
            _newValues(position) = _currentValues(i)
            position += 1
        Next
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        'Increment the counter every post back
        If Page.IsPostBack Then
            _startIndex += 1
        End If

        'Don't allow the counter to go outside the bounds of the array
        If _startIndex >= _currentValues.Length Then
            _startIndex = 0
        End If
        Me.StartIndex.Text = _startIndex 'Assign the value of the hidden field
    End Sub

    Public Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    'Dynamically set label / hidden data
        For i As Integer = 0 To _newValues.Length - 1 Step 1
            CType(Page.FindControl(String.Concat("Label", i), Label).Text = _currentValues(i)
            CType(Page.FindControl(String.Concat("Hidden", i), Hidden).Text = _newValues(i)
        Next
    End Sub

    Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
    'Dynamically set label / hidden data
        For i As Integer = 0 To _newValues.Length - 1 Step 1
            CType(Page.FindControl(String.Concat("Label", i), Label).Text = _currentValues(i)
            CType(Page.FindControl(String.Concat("Hidden", i), Hidden).Text = _newValues(i)
        Next
    End Sub

End Class

Then in your form:

<asp:Hidden ID="StartIndex" runat="server" Value="" />
<asp:Label ID="Label1" runat="server" Value="" />
<asp:Hidden ID="Hidden1" runat="server" Value="" />

<asp:Label ID="Label2" runat="server" Value="" />
<asp:Hidden ID="Hidden2" runat="server" Value="" />
etc...

This code (or at least a version of it) will build a number of label and hidden input fields that will be used to display data and persist data. Each time the page is posted, the start index will be incremented, which will change the start position of the new values. While the current values will be based on what is posted back from the hidden inputs.