Refreshing Listbox in VB.Net - vb.net

Question

I was wondering if there is any way to refresh the cont numbers in a listbox
i am adding data with the code
ListBox1.Items.Add
I have set up as button to remove selected data with the code:
For i As Integer = ListBox1.SelectedIndices.Count - 1 To 0 Step -1
ListBox1.Items.RemoveAt(ListBox1.SelectedIndices.Item(i))
Next
say my list box is like this
Zach
Barry
John
Nick
Brodie
if i deleted say barry how can i make the numbers change so john would be 2. etc

Answer 1

The BindingList can be helpful here since it can listen for changes in the list.
For example, create a Person class and override the ToString function to show the rank and the name.
Public Class Person
Property Name As String
Property Rank As Integer
Public Overrides Function ToString() As String
Return Rank & ". " & Name
End Function
End Class
In your form, declare the list and add the event handler:
Private people As New BindingList(Of Person)
Public Sub New()
InitializeComponent()
AddHandler people.ListChanged, AddressOf people_ListChanged
people.Add(New Person() With {.Name = "Zach"})
people.Add(New Person() With {.Name = "Barry"})
people.Add(New Person() With {.Name = "John"})
people.Add(New Person() With {.Name = "Nick"})
people.Add(New Person() With {.Name = "Brodie"})
ListBox1.DataSource = people
End Sub
Private Sub people_ListChanged(sender As Object, e As ListChangedEventArgs)
For i As Integer = 0 To people.Count - 1
people(i).Rank = i + 1
Next
End Sub
The ListChanged event just updates the ranking of each member as they as slotted in the list, which will automatically update the ListBox since the DataSource is coming from the people list.
A simple delete button to test the list, and the rankings are automatically updated in the people list, which automatically updates the ListBox:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If ListBox1.SelectedIndex > -1 Then
people.Remove(ListBox1.SelectedItem)
End If
End Sub

Answer 2

If you have some idea of GDI+ drawing, a more interesting approach is to set your ListBox's DrawMode to OwnerDrawFixed mode and listen to ListBox's DrawItem event, something like this:
C#
private void listBox1_DrawItem(object sender, DrawItemEventArgs e)
{
e.DrawBackground();
e.Graphics.DrawString((e.Index + 1).ToString() + ". " + listBox1.Items[e.Index].ToString(), listBox1.Font, Brushes.Black, e.Bounds);
}
VB.NET
Private Sub listBox1_DrawItem(sender As Object, e As DrawItemEventArgs)
e.DrawBackground()
e.Graphics.DrawString((e.Index + 1).ToString() & ". " & listBox1.Items(e.Index).ToString(), listBox1.Font, Brushes.Black, e.Bounds)
End Sub
Adding or removing any items to the ListBox will automatically renumber all the items.

Answer 3

You can use a List of string combined with the ListBox.
Dim NamesList1 As New List(Of String)
Private Sub Form_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
NamesList1.AddRange({"Zach", "Barry", "John", "Nick", "Brodie"})
FillListBoxItems()
End Sub
Private Sub FillListBoxItems()
ListBox1.Items.Clear()
For i As Integer = 0 To NamesList1.Count - 1
ListBox1.Items.Add(i + 1 & ". " & NamesList1.Item(i))
Next
End Sub
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
For i As Integer = ListBox1.SelectedIndices.Count - 1 To 0 Step -1
NamesList1.RemoveAt(ListBox1.SelectedIndices.Item(i))
Next
FillListBoxItems()
End Sub