Writing a passed Array via session into Label isn't working - asp.net

Question

I am trying to take an array of string (Filled from a listbox on a previous page and passed via Session) and display it in a label,this is how i got the array:
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles CheckOut.Click
Dim x = ListBox1.GetSelectedIndices.Count
Dim ListPNames(x) As String
Dim i As Integer
i = 0
For Each item As String In ListBox1.GetSelectedIndices
ListPNames(i) = (ListBox1.SelectedItem).ToString
i = i + 1
Next
Session("SlctdPhones") = ListPNames(x)
Response.Redirect("CheckOut.aspx")
End Sub
And this is how i am trying to display it :
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
Dim SlctdPhones() As String = CType(Session.Item("SlctdPhones"), Array)
Dim i As Integer
Label3.Text = ""
For i = 0 To SlctdPhones.Length - 1
Label3.Text += SlctdPhones(i).ToString() + Environment.NewLine
Next
End Sub
It is giving me an error :Object reference not set to an instance of an object. when it reaches the SlctdPhones.Length - 1 Line!!
i don't know how i can fix it ,also is my array code correct(Is everything being stored correctly in it?)

Answer 1

You declare the For loop like this:
For Each item In ...
But then never use the item variable in the body of the loop. Instead, you keep using the same SelectedItem property. You want to change that whole method to look like this:
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles CheckOut.Click
Dim PNames As New List(Of String)()
For Each index As Integer In ListBox1.GetSelectedIndices
PNames.Add(ListBox1.Items(index).Value)
Next
Session("SlctdPhones") = PNames
Response.Redirect("CheckOut.aspx")
End Sub
With that fixed, the Page_Load can do this:
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
Dim SlctdPhones As List(Of String) = TryCast(Session.Item("SlctdPhones"), List(Of String))
If SlctdPhones Is Nothing OrElse SlctdPhones.Length = 0 Then
'Something went wrong here!
Return
End If
Label3.Text = String.Join("<br/>", SlctdPhones.ToArray())
End Sub
But I'd really love to see you use a data control rather than stuffing <br/>s into a label. Here's markup for a ListView:
<asp:ListView ID="ListView1" runat="server">
<LayoutTemplate>
<ul>
<asp:PlaceHolder ID="itemPlaceholder" runat="server" />
</ul>
</LayoutTemplate>
<ItemTemplate>
<li><%# Container.DataItem.ToString() %></li>
</ItemTemplate>
<EmptyDataTemplate>
<p>Nothing here.</p>
</EmptyDataTemplate>
</asp:ListView>
And then Page_Load is even simpler:
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
ListView1.DataSource = Session.Item("SlctdPhones")
ListView1.DataBind()
End Sub

Answer 2

On display page, use Literal instead of Label
Dim SlctdPhones() As String = CType(Session.Item("SlctdPhones"), Array)
Dim result as String = string.Join("<br>", SlctdPhones) 'Instead of <br> try Environment.NewLine as well
YourLitetal = result
Hope this helps!