Ensure there is at least one item selected : ListBox « Windows Presentation Foundation « VB.Net Tutorial

1. VB.Net Tutorial
2. Windows Presentation Foundation
3. ListBox

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" Height="300" Width="300">
    <StackPanel>
        <ListBox FontSize="16" Height="150" Margin="5" Name="listBox1" SelectionMode="Extended">
            <ListBoxItem>List Item 1</ListBoxItem>
            <ListBoxItem>List Item 2</ListBoxItem>
            <ListBoxItem>List Item 3</ListBoxItem>
        </ListBox>
        <StackPanel HorizontalAlignment="Center" Orientation="Horizontal">
            <Label Content="_New item text:" VerticalAlignment="Center" Target="{Binding ElementName=textBox}"  />
            <TextBox Margin="5" Name="textBox" MinWidth="120" />            
        </StackPanel>
        <StackPanel HorizontalAlignment="Center" Orientation="Horizontal">
            <Button Click="btnAddListItem_Click" Content="Add Item" IsDefault="True" Margin="5" Name="btnAddListItem" />
            <Button Click="btnDeleteListItem_Click" Content="Delete Items" Margin="5" Name="btnDeleteListItem" />
            <Button Click="btnSelectAll_Click" Content="Select All" Margin="5" Name="btnSelectAll" />
        </StackPanel>
    </StackPanel>
</Window>
//File:Window.xaml.vb
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media

Namespace WpfApplication1
  Public Partial Class Window1
    Inherits Window
    Public Sub New()
      InitializeComponent()
    End Sub
    Private Sub btnAddListItem_Click(sender As Object, e As RoutedEventArgs)
      If textBox.Text.Length = 0 Then
        MessageBox.Show("Enter text to add to the list.", Title)
      Else
        Dim item As New ListBoxItem()
        item.Content = textBox.Text
        item.IsSelected = True
        item.HorizontalAlignment = HorizontalAlignment.Center
        item.FontWeight = FontWeights.Bold
        item.FontFamily = New FontFamily("Tahoma")

        listBox1.Items.Add(item)

        textBox.Clear()
        textBox.Focus()
      End If
    End Sub

    Private Sub btnDeleteListItem_Click(sender As Object, e As RoutedEventArgs)
      If listBox1.SelectedItems.Count = 0 Then
        MessageBox.Show("Select list items to delete.", Title)
      Else
        While listBox1.SelectedItems.Count > 0
          listBox1.Items.Remove(listBox1.SelectedItems(0))
        End While
      End If
    End Sub
    Private Sub btnSelectAll_Click(sender As Object, e As RoutedEventArgs)
      listBox1.SelectAll()
    End Sub
  End Class
End Namespace

16.27.ListBox
	16.27.1.	Bind String Array Resource to ListBox
	16.27.2.	Use Data Templates to Display Bound Data
	16.27.3.	CheckBox List
	16.27.4.	Convert the contents of a ListBoxItem to an instance of GridLength by using GridLengthConverter
	16.27.5.	Use the FontSizeConverter class to convert the content of a ListBoxItem to a value that represents the size of a font.
	16.27.6.	Convert contents of a ListBoxItem to an instance of Thickness by using the ThicknessConverter
	16.27.7.	DataTrigger, ListBox and user object
	16.27.8.	Add selected file to ListBox
	16.27.9.	This list box allows items to be selected in groups by using the SHIFT key and mouse or the CTRL key and space key.
	16.27.10.	Iterate through the selected items and remove each one
	16.27.11.	Ensure there is at least one item selected